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Chapter 1

Chemical Reactions & Equations
Chemical Equation
Chemical equation is a description of a chemical reaction
...
Balanced means that all
the atoms present among the reactants (the left side of the equation) were accounted for among the products
(the right side)
...
This is the reaction of turning oxygen and
hydrogen into water (unbalanced) :
H2 + O2 
 H2O
Notice that there are two hydrogens and two oxygens on the left side
...
For the equation to be correct, it must be balanced, so both sides have equal
amounts of atoms
...
When the equation is finally
balanced, it is :
2H2 + O2 
 2H2O
Now on both sides, there are four hydrogen atoms and two oxygen atoms
...


Moles
Number of particles equal to number of atoms present in 12 gm of C12 is 1 mole
...
023 ×
1023 particles is called a mole
...

This number, 6
...
022 × 1023
particles

Mole - volume
relationship

22
...
One mole of N2 gas will have gram molecular mass as __________, number of particles ________,
and volume at STP ______________?
A
...
022 × 1023, 22
...

Q
...
20, 60
...

1

Chemical Reactions & Equations

Class X - Chemistr y

Types of Chemical Reactions
All chemical reactions can be placed into one of six categories
...


Combustion: A combustion reaction is when oxygen combines with another compound to form water
and carbon dioxide
...
An example of this
kind of reaction is the burning of napthalene:
C10H8 + 12O2  10 CO2 + 4 H2O + heat

2
...
These reactions come in the general form of:
A + B  AB
One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide:
8Fe + S8  8FeS

3
...
These reactions come in the general form:
AB  A + B
One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas:
2H2O  2 H2 + O2

4
...
These
reactions come in the general form of:
A + BC  AC + B
One example of a single displacement reaction is when magnesium replaces hydrogen in water to make
magnesium hydroxide and hydrogen gas:
Mg + 2 H\O  Mg(OH)2 + H2

5
...
These reactions are in the general form:
AB + CD  AD + CB
One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide
to form lead (II) iodide and potassium nitrate:
Pb(NO3)2 + 2 KI  PbI2 + 2KNO3

6
...
The H+ ion in the acid reacts with the OH- ion in the base, causing the
formation of water
...

HA + BOH  H2O + BA
One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide:
HBr + NaOH  NaBr + H2O

2

Chemical Reactions & Equations

Class X - Chemistr y

Redox-Reactions
Redox reactions are those chemical reactions during which both oxidation and reduction take place
simultaneously
...
g
...


b)

Hydrogen is removed
...


d)

Oxidation number of an atom increases
...
(i
...
, it is an endothermic process)
...
g
...


Reduction
Reduction is that chemical process during which
a)

oxygen is removed
...


c)

electronation of either an atom or an ion take place
...
of an atom decreases
...

–
Cl + e– 
 Cl

+2
Fe+3 + e– 
 Fe

The tendency of an atom to undergo reduction decreases down the groups from top to bottom while it
increases along the periods from left to right
...


b)

which accept electron/electrons
...


d)

oxidise others but itself reduced
...
g
...

Identification
a)

Generally the names of an oxidising agent end either in “ate” or “ic”
...
g
...

HNO3 
 Nitric acid
...

K2Cr2O7 
 Potassium dichromate
...

e
...
,

c)

6
5
7
6
H 2SO 4 , HNO3 , KMnO 4 , K 2 Cr2 O7

Except carbon, all the non-metals are oxidising agents
...


Reducing Agent (R
...
)
A reducing agent is that atom or molecule :
a)

which undergo oxidation during reactions
...


c)

whose oxidation number increases
...
g
...


Identification :
a)

Generally the names of reducing agents end either in “ous” or “ide”
...

H2S 
 Hydrogen sulphide
...
N
...
H2 S ; HI
...
Cs is the strongest reducing metal
...


*

Highest O
...
= groups no
...


*

Lowest O
...
= group no
...
of the element in long form of P
...


4

Chemical Reactions & Equations

*

Class X - Chemistr y

(a) If the O
...
of a atom will be equal to its highest O
...
value then it will be an oxidising agent
...
N
...
N
...

(c) If the O
...
of an atom will be in between highest & lowest O
...
then the molecule will behave like
an oxidising as well as a reducing agent
...
A
...
A
...
N
...
N
...
N
...

2
Fe Cl2
R
...


3
F eCl3
O
...


1
Cu2O
R
...


2
CuO
O
...


Oxidation number
Oxidation number of an atom is either real or imaginary charge which appears to be associated with an atom
either in a molecule or an ion
...
It suggests the extent of oxidation and reduction of an atom
during reactions
...
, fraction or even zero
...
N
...
N
...


1 1
Na Cl

1  1
H Cl

O
...
of Na in NaCl = +1

O
...
of H = +1

O
...
of Cl in NaCl = –1

O
...
of Cl = –1

Calculation of oxidation number
1
...

Naº,

P4º,

Fº,

Caº

2
...


3
...
N
...


4
...
N
...

Li, Na, K, Rb, Cs are alkali metals
...
N
...

(c) O
...
of Al is always +3
...


Class X - Chemistr y

In combined forms
(a) O
...
of F is always –1
...
N
...
In interstitial hydrides it is 0
...
In peroxide its O
...
is –1
...
N
...


1
In super oxides it is  (eg
...
superoxide KO2)
...
g
...
Ozonide KO3)
...
N
...
But in interhalogen compounds it show +ve O
...
value
 1 1

Cl F

1

1

Br Cl

F always show –ve O
...
value
...


Higher O
...
of an atom of an element in a molecule or an ion can’t exceed its group no
...


7
...


Corrosion
Any process of deterioration (destruction) and consequent loss of a solid metallic material through an unwanted
chemical or electrochemical attack by its environment starting at its surface is called corrosion
...
More active metals are corroded more easily
...
Corrosion of iron is called rusting
...
xH2O and therefore it is in oxidation process for iron metal and
oxidising agent is oxygen in presence of weak acid (H2CO3)
...

Fe + 2H+ +

1
O
2 2

Fe2+ + H2O ; E0cell = 1
...

2Fe2+ +

1
O + 2H2O
2 2

Fe2O3 + x H2O

Fe2O3 + 4H+
Fe2O3
...


By coating with a suitable material (barrier protection)

2
...
g
...


3
...


By using artificial anode (Sacrificial protection) Galvanisation
...
When a fatty substance is exposed to air, its unsaturated components
are converted into hydroperoxides, which break down into volatile aldehydes, esters, alcohols, ketones, and
hydrocarbons, some of which have disagreeable odours
...
Saturated fats such
as beef tallow are resistant to oxidation and seldom become rancid at ordinary temperatures
...


In the reaction Zn + CuSO4 
 ZnSO4 + Cu, Zn is
(a) Oxidising agent
(b) Reducing agent
(c) Neutral
(d) Both oxidising and reducing agent

2
...

4
...


(d) + 1
(d) 8 × NA

Which of the following reactions is balanced ?
(a) N2 + 3H2 
 NH3

(b) 2H2 + O2 
 H2O

(c) H2 + Cl2 
 HCl

(d) 2N2 + 5O2 
 2N2O5


2KClO3 
 2KCl + 3O2 is

(a) synthesis reaction
(c) combustion reaction

(b) decomposition reaction
(d) disproportionation reaction

6
...
T
...
?
(a) H 2
(b) Ne
(c) CO 2
(d) NH 3

7
...
7 gm of sugar (C12H22O11) in order to sweeten his tea
...
mass of sugar = 342)
(a) 3
...
2 × 1021
(c) 0
...
6NO22

8
...


4
3

(b) +

4
3

(c) –

2
3

(d) +

2
3

Which of the following in a redox reaction ?
(a) NaCl + KNO3 
 NaNO3 + KCl
(b) CaC2O4 + 2HCl 
 CaCl2 + H2C2O4
(c) Mg(OH)2 + 2NH4Cl 
 MgCl2 + 2NH4OH
(d) Zn + 2AgCN 
 2Ag + Zn(CN)2

II
...

(ii) In the reaction KMnO4 
 MnCl2, the oxidation number of Mn _______________
...

(iv) _______________ is the cause for rusting of Fe
...

(vi) Formation of a positive ion from an atom is _____________
...


True / False
(i) 2CO + O2 
 2CO2 is a combination redox reaction
...

(iii) It is also a substitution reaction
...

(v) Oxygen is oxidising agent
...


Subjective Type Questions

1
...


Balance the following reaction :
C4H10 + O2 
 CO2 + H2O

3
...


Out of 1 gm O, 1 gm O2 and 1 gm O3 which has maximum number of oxygen atoms ?

5
...


6
...
of N:

NH3, N3H, N2O, NO, N2O5

(b) decreasing oxidation no
...


Multiple Choice Questions :
1
...
(c)
3
...
(d)
7
...
(b)
II
...
True / False
(i) False
(ii) True
IV
...

9
...


(b)

(iii) molecular weight

(iv) Corrosion

(iii) False

(v) True

(iv) True

1
...
023 × 1024
2
...
All have same no
...

5
...


3
...
(a) increasing oxidation no
...

+1

+5

+3

+7

H XO, H X O3 , H XO 2 , H XO 4
HXO4 > HXO3 > HXO2 > HXO
8

Chapter 2

Acids, Bases & Salts
Acids and Bases
1
...

(i)

Arrhenius Theory : Arrhenius defined acids as those compounds which give hydrogen ions in
aqueous solution, and bases as those compounds which give hydroxide ions in solutions
...
g
...

This definition can be applied only for those reactions which take place in aqueous solutions
...

Basicity or protonicity of acids : - It is the number of H+ ions furnished by a molecule of an acid
...
g
...

Dibasic acid : An acid furnishing two H+ ions e
...
H2SO4, H3PO3 etc
...
g
...

Acidity or Hydroxicity of base : It may be defined as the number of OH– ions furnished by a
molecule of a base
...

e
...
,

HCl + H2O ‡ˆ ˆˆ †ˆ H3O  Cl–
A1
B2
A2 B1

Equation


...
2

From the above observations we may conclude that every acid has a conjugate base and every
base has a conjugate acid
...

9

Acids, Bases & Salts

Class X-Chemistr y

Thus according to this theory the following conclusions can be drawn
...

(b) In aqueous solutions H ions exist as hydrated ions or H3O+ (H+
...

(c) Even ions may act as acids or bases
...

H3O+ + OH–
A-1 B-2

H2O + H2O

B1

A2

A1

B2

(e) The strength of acids (or bases) depends on the medium which acts as base (or acids)
HCl + H2O  H3O + Cl–
HCl + NH3  NH4 + Cl–
HCl + Benzene  No reaction
Acidic nature of HCl is greatest in ammonia and least in benzene
...
e
...
CCl4, CS2, Benzene
...
g
...

(iii) Protophillic - Solvents which have a greater tendency to accept proton e
...
H2O, R-OH, liquor
NH3
...

The ionization of strong acids in water may be represented as below :
HCl + H2O ƒ

H3O+ + Cl–

H2SO4 + H2O ƒ H3O + HSO4–
Thus all strong acids (e
...
HNO3, HCl, H2SO4, HClO4) react almost completely to form H3O+ ion
...
i
...
Acidic levels for all acids are same
...
Thus the relative acidic strengths or basic
strengths in aqueous solutions cannot be compared
...
(This is because of poor proton accepting character of acetic acid)
...

The degree of dissociations of a number of acids dissolved in glacial acetic acid has been determined and it
is found that the acidic strength order is
10

Acids, Bases & Salts

Class X-Chemistr y

HClO4 > HI > HBr > H2SO4 > HCl > HNO3 > H3O+ > HSO4– > H3PO4 > HF > CH3COOH > H2CO3 > H2S
> NH4+ > HCN

Lewis Concept of Acids And Bases
According to Lewis, an acid is any species which is capable of accepting a pair of electrons and a base is a
species that is having a lone pair of electrons for donations
...

Thus all Bronsted-Lowry bases are Lewis bases while all Bronsted-Lowry acids are not Lewis acids
...
This means all electron deficient molecules
can act as Lewis acids e
...

BF3, BBr3, AlCl3, FeCl3, GaCl3 etc
...
e
...
SnF4, SnCl2, SnCl4, PF3,
PF4, SF4, TiCl4 etc
...
e
...
Cu2+ + 4NH3

[Cu (NH3)4]2+
...
g
...


(ii) Molecules containing one or more unshaired pairs of electrons (Lone pairs) e
...
H2O, NH3, ROH,
NX3, R2S, etc
...

(iii) Multiple bonded compounds which can donate the pair of electrons
...
g
...


Salt
A substance which ionizes in water to produce ions other than H+ and OH– is called a salt
...
These are prepared by the neutralization of strong acid and strong base
...
g
...

Acidic Salts : Those salts whose aqueous solutions turn blue litmus red are called Acidic salts
...
g
...

Basic Salts : Those salts whose aqueous solutions turn red litmus blue are called basic salts
...
e
...
Na2CO3, CH3COONa
Mixed salts : Salts formed by the neutralization of one acid by two bases or one base by two acids are
called mixed salts
...
g
...
g
...
(NH4)2 SO4
...
Al2 (SO4)3
...
e
...

K4 [Fe(CN)6]
Li (AlH4)

pH:
It may be defined in number of ways
...


(ii) It can also be defined as the negative logrithm of its [H+] ion concentrations
pH = –log[H+]
pH values do not give instantaneous idea above the relative strengths of the solution

pOH :
It may be defined as the negative logrithms of hydroxyl ions concentration
pOH = –log (OH–)
...


Some Important Chemicals
Bleaching Powder (CaOCl2)

Preparation
In Hasen-Clever Plant
Ca(OH)2 + Cl2  CaOCl2 + H2O

Properties
(1) It is yellowish white solid having chlorine like smell
(2) Bleaching powder decomposes to form O2
2CaOCl2

CoCl2

2CaCl2 + O2

(3) When reacted with H2O liberates Cl2
...

CaOCl2 + H2SO4  CaSO4 + H2O + Cl2
(5) It reacts with carbondioxide to form calcium carbonate and Cl2
...
This I2
can be estimated by Na2S2O3 thus we can measure the available chlorine in bleaching powder
...
For use in outdoor
swimming pools, it can be used as a sanitizer in combination with a cyanuric acid stabilizer
...
Calcium does make the water ‘hard’ and tends to clog
up some filters, for this reason Sodium hypochlorite is preferred
...

Sodium Hydroxide (NaOH)

Preparation
(1) Soda lime process, causticisation process or Gossage process
Na2CO3 + Ca (OH)2

80 - 90ºC

2NaOH + CaCO3

(2) Castner kellner proces - Electrolytic process
Electrolyte  Brine (NaCl Solution in water)
Anode  Graphite
Cathode  Iron rods and Mercury acts as intermediate cathode by induction
...

(2) Sodium hydroxide decomposes on heating to form sodium, hydrogen and oxygen
...

(a) 2NaOH + CO2  Na2 CO3 + H2O
(Sodium carbonate)
(b) 2NaOH + SO2  Na2SO3 + H2O
(Sodium sulphite)
(c) 2NaOH + SiO2  Na2SiO3 + H2O
(5) Metals like Zn, Al, Sn, Pb etc
...
Even silicon displaces
hydrogen from NaOH
...

(a) 4S + 6NaOH  2Na2S + Na2S2O3 + 3H2O
(Sodium thiosulphate)
(b) 4P + 3NaOH + 3H2O  3NaH2PO2 + PH3
(Sodium hypophosphite)
(c) Cl2 + 2NaOH (cold and dilute)  NaCl + NaClO + H2O
(Sodium hypochloride)
(d)

3Cl2 + 6NaOH (hot and conc
...
as metal hydroxides
...

14

Acids, Bases & Salts

Class X-Chemistr y

(a) AlCl3 + 3NaOH  Al(OH)3 + 3NaCl
Al (OH)3 + NaOH  NaAlO2 + 2H2O
(b) Zn SO4 + 2NaOH  Zn (OH)2 + Na2SO4
Zn(OH)2 + 2NaOH  Na2ZnO2 + H2O

Uses
Used as strong base in chemical industry
...


Plaster of Paris
Quick-setting gypsum plaster consisting of a fine, white powder, calcium sulfate hemihydrate, which hardens
when moistened and allowed to dry
...
With an additive to retard the set, it is called wall, or hard-wall,
plaster
...
2H 2 O 
 CaSO4
...
Plaster of paris is also used to precast and hold parts of ornamental plasterwork placed
on ceilings and cornices and is used in medicine to make plaster casts to immobilize broken bones while they
heal
...
The speed at which the plaster sets gives the
work a sense of immediacy and enables the sculptor to achieve the original idea quickly
...
For example, in
copper (II) sulphate, there are five moles of water per mole of copper sulphate: hence its formula is
CuSO4
...
This water is responsible for the colour and shape of the crystalline form
...


CuSO4
...
Because it has long been known
and is widely used, the salt has many other names including sodium hydrogencarbonate, sodium bicarb,
baking soda, bread soda, cooking soda, bicarb soda, saleratus or bicarbonate of soda
...

Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder
...
It is a component of the mineral natron and is found
dissolved in many mineral springs
...
It is also produced
artificially by passing CO through aqueous sodium carbonate solution
...
Also used as antacid in medicines and as an absorbant for moisture and
odour
...

15

Acids, Bases & Salts

Class X-Chemistr y

Washing Soda
Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid
...
It has a cooling alkaline taste, and can be extracted from the ashes of many plants
...

Solvay’s ammonia process : In this process Brine (NaCl) solutions is saturated with ammonia and carbon
dioxide to get the precipitate of NaHCO 3 which on heating gives Na 2 CO 3
...
In chemistry, sodium carbonate
is often used as an electrolyte
...
It competes with
the ions magnesium and calcium in hard water and prevents them from bonding with the detergent being
used
...

Called Washing Soda or Sal Soda in the detergent section of stores, it effectively removes oil, grease, and
alcohol stains
...
Sodium carbonate is widely used in photographic processes as a pH regulator to
maintain stable alkaline conditions necessary for the action of the majority of developing agents
...


ASSIGNMENTS
Multiple Choice Questions
1
...


(c) Lewis acid

(d) None of these

(c) Neutral

(d) Amphoteric

(c) both of these

(d) none of these

(c) lower fatty acids

(d) higherfatty acids

(b) Basic

(b) reducing agent

Soaps are sodium salts of
(a) carbonic acid

16

(b) Bronsted acid

Bleaching powder acts as
(a) oxidising agent

5
...


(c) tribasic acid

AlCl3 is
(a) Arrhenius acid

3
...

7
...


9
...


Which of the following is a weak electrolyte ?
(a) NH4Cl
(b) NH 4 OH

Class X-Chemistr y

(c) NaOH

Which of the following is the best conductor of electricity ?
(a) 1 MHCl
(b) 1 M H2CO3
(c) 1MH3SO4

(d) HCl
(d) 1MH2SO4

The reaction of water with ammonia is given by the following equation

H2O + NH3 ‡ˆ ˆˆ †ˆ NH4+ + OH
In this reaction water behave as (a) neutral
(b) base
(c) acid

(d) both acid and base

The compound that is not a Lewis acid is
(a) BF3
(b) BaCl2

(d) SnCl4

(c) AlCl3

Which of the following will not change red litmus blue ?
(a) B(OH)3
(b) NaOH
(c) Ca(OH)2

(d) Ba(OH)2

Fill in the blanks
1
...


2
...


3
...


4
...


5
...


True / False
1
...


2
...


3
...


4
...


5
...


Subjective Type Questions
1
...


Calculate the pH of 0
...

What will be the nature of solution obtained by mixing 200 ml of 0
...
2 M
H2SO4 ?

3
...


Write the reaction for formation of sodium hypophosphite
...


Which of the following is a Bronsted-Base ?
I–, H3O+, HCl, NH4+
Complete the reaction :

6
...
2H2O  373K




(iii) NaCl + NH3 + H2O + CO2 


(iv) NaHCO3 


(v) CuSO4
...

6
...

7
...

8
...

9
...

10
...


True

5
...

higher
2
...

NaCl
4
...

SO 4 2–
True / False
1
...


False

3
...


1
...

3
...

acidic
...


4
...


5
...


i)

Ca(OH)2 + Cl2 
 CaOCl2 + H2O

 373K
ii) 2CaSO4
...
H2O + 3H2O

iii) NaCl + NH3 + H2O + CO2 
 NaHCO3 + NH4Cl

iv) 2NaHCO3 
 Na2CO3 + H2O + CO2

v) CuSO4
...
Metals are malleable : Metals can be hammered or beaten into thin sheets without breaking
...
Gold (Au), silver (Ag) are highly
malleable elements
...
Metals are ductile : Metals can be melted and drawn into thin wires
...
Silver (Ag), copper (Cu), aluminum (Al) are very ductile, very thin wires can be
made out of these elements
...
Metals are good conductors of heat and electricity : In metals, the bonds are formed by excess or
free electrons moving around large array of atoms
...
Silver (Ag), copper (Cu), aluminum (Al) are good conductors of heat and electricity
...
Metals have lustre : Metals generally can be highly polished
...
This gives metal the characteristic metallic lustre
...

5
...

Their bonds do not break easily as the electrons are shared over an array of metal atoms
...

6
...
Mercury (Hg) is the only exception - it is liquid
at room temperature
...
Only sodium (Na) and potassium (K) have densities less
than water
...

7
...
But Zinc (Zn) is an exception
...
Melting and boiling points : All metals, other than sodium (Na) and potassium (K), have high melting
and boiling points
...
The melting
point of iron is about 1540°C
...
Solubility of metals : Pure metals are insoluble in solvents like water or in any organic solvent
...

10
...
Thus metals are
sonorous
...

Chemical properties
1
...

The atoms can therefore loose electrons while forming compounds
...
Reaction with oxygen : All metals react with oxygen to form metal oxides
...
For example Fe can form oxides FeO,
Fe2O3, Fe3O4, etc
...

3
...
Hydrogen gas is released in this reaction
...

19

Metals and Non-Metals

Class X - Chemistr y

(i) Sodium reacts with water at ordinary room temperature, or even cold water
...
But Mg reacts with
hot water easily to form MgO
...

Mg + H2O  MgO + H2
Since heat is required for starting the above reaction, it means that Mg is less reactive than Na
...
Zinc forms ZnO (zinc oxide) and hydrogen are formed
...
Iron has to be heated to a red-hot condition and steam
has to be introduced for Fe to react with water (steam)
...

3Fe + 4H2O  Fe3O4 + 4H2
(v) Copper metal does not react with water or steam
...
Reaction with dilute acids : Most metals react with dilute acids by replacing hydrogen and forming a
salt
...
The rate of reaction depends on the
reactivity of the metal
...

With dilute hydrochloric acids, metals react to give metal chloride and hydrogen, e
...
g
...

Nitric acid is an oxidizing acid and releases O from its NO3– radical, hence its reaction with metals does
not lead to metal-salt and hydrogen
...
Reactions with salt solutions : Reactivity of metals determine which salt is formed when a metal is
added to a salt solution
...
These are
called displacements reactions, e
...
,
CuSO4 + Zn  Cu + ZnSO4
6
...
Other metals do
not react with H easily
...
g
...
Metals as reducing agents : Metals have excess unbound electrons and are able to give these electrons easily
...
For example Na gives off an electron to any other substance which is forming a bond with itself
...

20

Metals and Non-Metals

Class X - Chemistr y

Non metals
1
...
Non-metals break into pieces when hammered or stretched
...
Brittleness is a characteristic property of non-metals
...
Non-metals are not ductile : Non-metals cannot be melted and drawn into thin wires
...
Thus the bonds between atoms in the elements are weak and they snap when
stretched
...

3
...
Other than graphite, which is an allotropic form of carbon, none
of the non-metals are good conductors of heat and electricity
...

4
...
Hence they
cannot be polished and they do not have any lustre
...
Only graphite
can be polished to some degree
...

5
...
Some
non-metals like carbon, sulphur, phosphorus are solids at room temperature
...
Most other non-metals are gaseous at room temperature
...
Carbon in its allotropic form of diamond is an exception here; diamond is the hardest substance
found in nature
...
Melting and boiling points : All non-metals, have low melting and boiling points
...
Graphite and diamonds have high melting points, but these are exceptions in the
non-metals
...
Solubility of non-metals : Non-metals are soluble in some chemical or organic solvents
...

8
...
This means that in non-metals, the atoms are not strongly bound
...

9
...
Thus non-metals are not sonorous
...
The idea of electro-valency or ionic bond was first proposed by
W
...
Atoms of elements, specially those of Group 1 and Group 2 of the periodic table can
outright transfer one or two electrons from their valency shell to the valency shell of some other atoms of the
elements of Group 16 and 17
...

Now, the atom which loses electron (or electrons) becomes positively charged with the formation of a cation,
while the atom which gains electron(s) becomes negatively charged with the formation of anion
...
e
...
,
21

Metals and Non-Metals

Class X - Chemistr y

Formation of sodium chloride
The electronic configuration of Na and Cl atoms along with their nearest noble gases neon and argon are as
follows :
Atom

Electronic structure

Noble gases

Na

1s2 2s2 2p6 3s1

10

Ne

1s2 2s2 2p6

Cl

1s2 2s2 2p6 3s2 3p5

18

Ar

1s2 2s2 2p6 3s2 3p6

11
17

Electronic structure

Na atom has one electron in the outermost 3s orbital i
...
, it has one electron excess in its valence shell, then
the neon atom
...
e, Cl atom has one electron
less in its valence shell than the argon atom
...
e
...
On the other hand,
Cl atom takes that electron and acquires the structure of argon
...

The cations like Na+ and anions like Cl– interact and as a result of electrostatic attraction between Na+ and
Cl–, stable crystal of sodium chloride is formed
...


Characteristics of Ionic Compounds
(1) Physical state : An ion can attract its oppositely charged ion from any direction
...
Hence ionic compounds are solids at room temperature
...

(3) Molecules of ionic compounds are polarised : Each ion pair (C+ A–) in an ionic compound is polar
...
This is
because of the fact that the ions are stationary in the ionic crystal and the cations and anions are held
together by strong electrostatic force
...
The freely moving ions permit electrical conductance
...
P
...
P
...
Thus,
NaCl melts at 820ºC and boils at 1600ºC
...
They react readily
with oxygen, carbon di-oxide and moisture of air
...
These metals occur in nature in the form of their compounds
...
These metals are also not found in nature
in free state, but they occur in nature as various types of compounds such as oxides, carbonates,
sulphides etc
...
They are not
attacked by oxygen, moisture or CO2 of atmosphere
...
Some of the forms in which metals occur in nature are given in following table
...
2H2O
CuFeS2
ZnS
PbS
FeCO3
CuCO3
...
MgCO3
CaSO4
...
A mineral may contain one or more than one metallic compounds
...

A metal may be present in a number of minerals, but all minerals are not suitable for the extraction of metals
economically on a large scale
...
All ores are minerals but all the minerals are not ores
...
They are always contaminated with rocky and earthly impurities
known as gangue or matrix
...


Metallurgical Processes
Metallurgy is the science and technology employed for the extraction of metals economically on a large scale
from their respective ores
...
(i) Concentration or
dressing of ore, (ii) Calcination, (iii) Roasting, (iv) Smelting and reduction, (v) Refining
...
Concentration or dressing of ore
The ore which is mined, usually contains large amount of rocky impurities such as sand, clay, lime stone
etc
...
Consequently, before the extraction of the metal, it is essential to increase
the metallic content of the ore by removing the gangue as far as possible
...

(i) Gravity separation – washing with water : This process is applied where there is well marked
difference in the densities of the gangue and the ore
...
This process of concentration is based
on the different wetting characteristics of the sulphide particles and the particles of gangue present
in the ore
...

The powdered ore is allowed to fall on a rubber belt moving round two rollers
...

(iv) Chemical method : In this process the desired metallic component in the ore is dissolved selectively
by digesting the powdered ore with a suitable reagent
...
From the aqueous solution thus obtained, the derived metallic component is regenerated
...
Calcination
Calcination is the process in which the concentrated ore is heated strongly below its fusion temperature
in absence or limited supply of air
...
, are removed from the ores
...
(c)
The ore becomes porous
...

calcination
ZnCO3 
 ZnO + CO2 ;

calcination
MgCO3 
 MgO + CO2 

3
...

Zinc blende on being roasted is converted to oxide and sulphate,
2ZnS + 3O2 = 2ZnO + 2SO2 ,

ZnS + 2O2 = ZnSO4

4
...
The important methods of reduction in
metallurgy are given below :
(1) Carbon reduction process :
The metals which are moderately electro positive, such as Zn, Fe, Sn, Pb etc
...
Carbon reduction process is employed in the extraction of such metals
...
Carbon monoxide which is produced by the incomplete
combustion of coke, can also act as reducing agent
...
e
...
,
Fe2O3 + 3C  2Fe + 3CO 
MgCO3  MgO + CO2,
MgO + C  Mg + CO
(2) Self reduction
This process of extraction of metals is employed in case of the sulphide ores of lead and copper
...
The oxide and sulphate thus formed react with the
unchanged sulphide at high temperature in absence of air to produce metals
...

24

Metals and Non-Metals

Class X - Chemistr y

2Cu2S + 3O2 = 2Cu2O + 2SO2

Cu2S + 2Cu2O = 6Cu + SO2

Cu2S + 2O2 = Cu2SO4

Cu2S + Cu2SO4 = 4Cu + 2SO2

(3) Electrolytic reduction
The strongly electro-positive metals such as K, Ca, Na, Al, Mg are very active
...
Moreover, even if the metal is formed, carbon reacts with the
metal produced to form carbide at high temperature
...

e
...
, In the extraction of sodium or potassium, fused hydroxides of the metals are used as electrolytes
...


At cathode :
At anode :

NaOH
 Na+ + OH–
Na+ + e  Na
Cl– – e  Cl
Cl + Cl  Cl2 

Flux and Slag
The flux is a substance which reacts with the gangue during smelting to form an easily fusible compound
which can be removed from the molten metal easily
...

Thus,

Flux

e
...
,

SiO2  CaO 
CaSiO3
acidic
impurity

+

Gangue

basic
flux



Slag

slag

5
...
They may contain small amounts
of impurities of other metals, dissolved oxides, sulphides, carbon etc
...

The process of refining vary from metal to metal according to the nature of the impurities present in the
crude metal
...

An electrolytic cell is set up by using blocks of crude metals as anode and thin strips of pure metal as
cathode
...
On passing electric current
pure metal is deposited on the cathode and an equivalent amount of the metal gets into the solution from
the anode
...

25

Metals and Non-Metals

Class X - Chemistr y

Reactivity Series
In chemistry, the reactivity series is a series of metals, in order of reactivity from highest to lowest
...


Metals

Metal Ion

K
Na
Ca
Li
Ba
Sr
Mg
Al
Mn
Zn
Cr
Fe
Cd
Co
Ni
Sn
Pb
H2
Sb
Bi
Cu
Hg
Ag
Au
Pt

K+
Na+
Ca2+
Li+
Ba2+
Sr2+
Mg2+
Al3+
Mn2+
Zn2+
Cr2+
Fe2+
Cd2+
Co2+
Ni2+
Sn2+
Pb2+
H+
Sb3+
Bi3+
Cu2+
Hg2+
Ag+
Au3+
Pt+

Reactivity

reacts with water

reacts with acids

included for comparison

highly unreactive

A metal can replace metals listed below it in the activity series, but not above
...


A metal which occurs in free state is
(a) calcium
(b) iron

(c) silver

(d) sodium

2
...


Floatation process is used to concentrate
(a) oxide ores
(b) sulphide ores

(c) carbonate ores

(d) silicate ores

A mineral which contain sulphur is
(a) magnetite
(b) calamine

(c) zinc blende

(d) bauxite

Calcination is carried out in absence of
(a) hydrogen
(b) nitrogen

(c) air

(d) none of these

Which is amphoteric oxide ?
(a) FeO
(b) ZnO

(c) CO 2

(d) NO

4
...

6
...


Class X - Chemistr y

Aluminium react with
(a) cold water
(c) steam

(b) hot water
(d) do not react with H2O

8
...


Which of the reaction will not occur ?
(a) MgSO4 (aq) + Cu(s) 
 CuSO4(aq) + Mg(s)
(b) CuSO4(aq) + Fe(s) 
 FeSO4(aq) + Cu(s)
 BaSO 4(aq )  Mg (s)
(c) MgSO 4(aq )  Ba (s ) 

(d) FeSO4(aq) + Zn(s) 
 ZnSO4(aq)+ Fe
10
...


The rocky impurities present in minerals are called _____________
...


In the thermite process _____________ is used as reducing agent
...


Impurities in the ores are usually removed by adding _____________
...


MgO is _____________ basic than CuO
...


Al react with boiling water liberating _____________
...


All ores are minerals, but all minerals are not ores
...


Na/K is not found in free state in nature
...


Metallic sodium is kept under kerosene
...


Galena is an oxide ore
...


Metallic Na or Ca is obtained by carbon reduction process
...


Explain the formation of CaCl2

2
...

Now, answer the following questions :
(a) Which has more oxidising power - Mg or Fe ?
(b) Which one can be precipitated from its sulphate solution by adding the other metal - Cu or Zn ?

28

Metals and Non-Metals

Class X - Chemistr y

(c) Which is expected to occur in free state in nature - Na or Cu ?
(d) Which will you select for the extraction by the electrolytic reduction process - Mg or Fe ?
(e) Which one not expected to be extracted by carbon reduction process - Na or Fe ?
3
...

(b) Arrange Na, Zn, Cu, Ca, Al in order of increasing electro-positive character
...

(d) Arrange Na, K, Fe, Ag, Cu in order of increasing reactivity
...


Name the metals having the following ores – (i) Chalcopyrites, (ii) Magnetite (iii) Calamine
(iv) Malachite
...


Distinguish between :
(i) Calcination and Roasting
(ii) Self reduction and Carbon reduction
...

(ii) Na/K is not found in free state in nature
...

(iv) Galena is an oxide ore
...


Subjective Questions
1
...


The electro-positive character of metals is in the following order –
Na > Mg > Al > Zn > Fe > H > Cu > Pt
...


(a) Arrange the oxides in order of increasing basic strength – MgO, Na2O, CaO, ZnO
...

(c) Arrange Mg, Al, Fe, Cu in order of increasing reducing power
...


4
...


5
...


(c)

2
...


(b)

4
...


(c)

6
...


(c)

8
...


(a)

10
...


3
...


Introduction
Carbon is an element truly which is a class by itself
...
One would expect carbon to use each of the four valence electrons in the
formation of chemical bonds and in this way achieve an octet of electrons
...
The true uniqueness of carbon comes, however, with the ability of carbon atoms to bond
with themselves
...
Pure
carbon occurs as several different allotropes, or structures which differ only in the way the atoms are
arranged
...
The chemistry of carbon compounds is so diverse that an entire field of organic
chemistry is devoted to the chemistry of this one element
...
In the diamond structure, each carbon atom is covalently bonded to four
others and has a tetrahedal geometry
...
This is reflected in the
chemical properties of diamond
...
Diamond
is denser than graphite and has a density of 3
...
Related to the diamond structure is the silicon carbide structure
...

Graphite
Graphite is second allotrope of carbon
...
However, in the case of graphite, the atoms are arranged in layers
...
Of the three bonds,
two are single bonds and one is a double bond
...
33
...
An unusual property of graphite is that it is electrically conductivity
...
22 grams per cubic centimeter
...

Fullerenes
Diamond and graphite used to be considered the only allotropes of carbon
...
One example includes C60, which is shown to the left
...
However, the molecule contains both five-membered as well as six-membered rings
...


The structure of diamond

The structure of graphite

The structure of C60 Buckminsterfullerene

BONDING IN CARBON
Carbon has electronic configuration 1s2 2s2 2p2
...
To complete its octet it shares 4
electrons with other elements to form four bonds, i
...
why carbon
is tetravalent
...
If we consider the formation of methane (CH4 )
carbon shares one electron each with four hydrogen atoms to form
four single bonds
...
Carbon readily forms
bonds with hydrogen, oxygen, nitrogen, sulfur, and the halogens
...
Such structures have a
tetrahedral geometry
...
Carbon also forms a series of
compounds with oxygen
...
Carbon
dioxide is formed in huge quantities by the combustion of fossil fuels
...
Dry
ice is composed of frozen carbon dioxide
...

In the carbon dioxide molecule, the oxygen atoms are each joined to the carbon atom by double bonds
...
Carbon monoxide is formed by the incomplete
combustion of fossil fuels
...
Like carbon dioxode, carbon monoxode is a colorless, odorless gas
...
Carbon monoxide is
also a very good ligand, and combines with many metals to form compounds called metal carbonyls
...
It is believed to have a linear shape
...

32

Addition Reactions

2
...
Elimination Reactions

Carbon and its Compounds

1
...

CH2 = CH2 + HBr  CH3 – CH2 – Br

(a) Electrophilic addition reactions
CH2 = CH2 + Br2  CH2 – CH2 – Br
Br

(b) Nucleophilic addition reactions
CH3CHO + HCN  CH3CH

OH
CN

(c) Free radical addition reactions
CH3 – CH = CH2 + HBr
2
...


(b) Electrophilic substitution reactions
...

3
...
Most commonly, loss of atoms
or groups occurs from adjacent carbon atoms to yield an olefin
...
KOH

CH2 = CH2 + HCl

Rearrangement: Rearrangement reactions involve either the migration of functional group to another positions
in the molecule containing a double bond or change of the sequences of atoms forming the basic carbon
skeleton of the molecule to form a product with the new structure
...
g
...


These compounds contain straight or branched chain of carbon atoms and are called as open chain or
acyclic compounds
...
e
...
, alkanes
(b) Unsaturated compounds - in which double or triple bonds are there
...
g
...

2
...
These are of two types
(i) Homocyclic compounds where the atoms are mostly carbon and hydrogen only
...
g
...
e
...
g
...
Later on the compounds with alternate single and double bonds were
called aromatic compounds
...
e
...
Also such systems should
be cyclic and resonance should be possible in them
When

n=0



2 e–

n=1



6 e–

n=2



10 e–

n=3



14 e–

Hence systems containing 4e– or, 6e– or 10e– are said to be following the Huckel Rule
e
...




Cyclopropenyl cation
(2 electron)

Benzene

Naphthalene

(6 electrons)

(10 electrons)

Anthralene
(14 electrons)

These are all aromatic compounds
...

I Common Name System
II IUPAC System of Nomenclature
...

Ex
...

PRIORITY LIST

35

Carbon and its Compounds

S
...


Functional group

Class X-Chemistr y

Formula

Family name

Substitution

1
...


Carboxylic acid

*
–COOH

Akanoic acid or

Carboxy

3
...


Ester

5
...


Acid amide

7
...


Aldehyde

9
...


Alcohol

–OH

Alkanol

Hydroxy

11
...


Thiols

–SH

Alkane thiols

Sulphamyl

13
...


Alkene, alkyne

C = C, C C

Alkene, alkyne

15
...


–X

17
...


Those functional gps which have been marked (*) if they behave like main functional groups
then there carbon atom must be included in the main chain
...


Those functional gps which have been marked (*) if they behave like substituents then their
carbon atom should not be included in the main chain
...


If CHO gp is the only substituent then its carbon atom may or may not be included in the main
chain
...

1
...

2
...

36

Carbon and its Compounds

Class X-Chemistr y

3
...

1
...
CH3 – CH – CH = CH – CONH2
OH

Main Functional group = –CONH2
Subsidiary = –C = C–
Substituent = –OH
...
CH3 – CH = CH – CH – COBr
CH = CH2

Main = –COBr
Subsidiary = C = C
Substituent = NIL
Step-II: Identification of main chain
Following points should be considered for choosing the main chain
...
The main chain must contain maximum number of main functional groups
...
It must contain maximum number of subsidiary groups
...
The main chain must contain maximum number of substituent carrying carbon atoms or side
chain carrying carbon atoms
...
The main chain must contain maximum number of carbon atoms
...

wrong chain

correct chain

1
...

correct chain

2
...

correct chain

3
...


Chain–3

O

O

CH3 – C – CH2 – CH – C – CH3
CH2 – Br

Chain–1

Chain–2

Here Chain–1 is correct chain
...

O

5
...
This is because it contains the main functional group, the
subsidiary group
Wrong chain

6
...
e
...

Step-III: Numbering the Main Chain
Numbering of the main chain is done according to :
Lowest Number Rule : After selecting the continuous main chain, the numbering is done in such
a manner that :
(a) the main functional group gets the lowest number
(b) the second lowest number is given to the subsidiary groups
(c) the third lowest number is given to the substituent carrying carbon atom or side chain carrying
carbon atom
...

1

2

Incorrect

3

1
...
CH3 – CH = CH – CHO
4

38

3

2

1

Correct

Carbon and its Compounds

1

Class X-Chemistr y

2

3

4

4

3

5

Incorrect

6

3
...
CH3 – CH2 – CH2 – CH2 – CH
3
4
5
2

Correct

1

2

1

Incorrect

CH = CH2
4

O

1

3

2

O

4

5

Incorrect

6

5

5
...
CH3 – CH – CH – CH = CH2
5

3

4

1

2

OH

Br

Correct

Lowest Set Rule at the First Sight of Difference : If more than one main functional group or substituents
are present in the chain, then their positions are noted and the sets are made of all possible numberings
...
The preferred numbering is the one which has the lowest term
in the set at the first point of difference e
...

2

1

1
...

Therefore set - 2 is preferred
...


3

2

4

5

6

7

8

9

10

C–C–C–C–C–C–C–C–C–C
10

9

8

C

7

C

6

5

Term - I

4

3

2

C

Term - II

1

Set - 1
Set - 2

Term - III

Sum Rule :

Set -1

3

4

9

set - 1 : 3 + 4 + 9 = 16

Set -2

2

7

8

set - 2 : 2 + 7 + 8 = 17
...

According to sum rule set - 1 is correct numbering
...

39

Carbon and its Compounds

Class X-Chemistr y

Step - IV: Writing the name
This part consists of
(a) Noun String (Family Name)
(b) Adjective String (Substituents or Side chains)
The adjective string is written first and then the noun string e
...

2

3

1

1
...

4

2

3

1

2
...

6

5

3

4

2

1

3
...

5-Bromo, hex-3-en-2-ol
...
CH3 – C – CH2 – CH – C – CH3
CH2 – Br

Adjective string = 2-Bromo methyl
Noun = Hexan -2, 5-dione
3-Bromo methyl, hexan -2, 5-dione
...


2O

CH = CH2
4

Adjective String = 3-Butyl
Noun String = Pent-4-en-2-one
...
CH3 – CH – CH – CH = CH2
Br OH
Adjective string 4-Bromo
Noun string pent-1-en-3-ol

4-Bromo, pent-1-en-3-ol
...
CH3 – CH – CH2 – CH – CN
CH = CH2

Br

4

3

Adjective String = 2-[2- Bromo Propyl]
Noun String : But -3-ene-1-nitrite
...


Nomenclature of Specific Families (Few selected)
1
...
g
...

CH3
CH – CH3

1
...


2
...

41

Carbon and its Compounds

2
...

If substituent/side chain present on alkanoante part write before writing the alkanoate part
CH3 – C – O – CH3 Alkyl
O

Methyl ethanoate

Alkanoate
4

2

3

1

CH3 – CH = CH – C – O – CH2CH3
O

3
...

R–NH – R
Name : N-alkyl, alkanamine
1
...
The alkanamine part must satisfy all the conditions for main chain
CH3–NH–CH2 CH3
N-methyl ethanamine
2

3

CH3 – CH2 – NH – CH – CH3
CH3

1

N-Ethyl, propan-2-amine
...


Tertiary Amines : Where the nitrogen atom is attached to 3-carbon atoms is called t-amines
...
[when alkyl groups attached to nitrogen are same] e
...

1
...


Class X-Chemistr y

N-Substituted Amides : Where in an amide molecule an alkyl group is attached on the nitrogen atom,
such molecules are called N-substituted amides e
...

R – C – NH – R

N-Alkyl

O
Alkanamide

N-Alkyl alkanamide
...


CH3 – C – NH – CH3
O

N-Methyl ethanamide
2
...


CH3 – CH – C – NH – CH3
Br

O

N-Methyl-2-bromo propanamide
4
...


43

Carbon and its Compounds

Class X-Chemistr y

Structural Isomerism : Compounds which have the same molecular formula but different structures (i
...
,
different arrangement of atoms within the molecule) are called structural isomers and the phenomenon is
called structural isomerism
...

Butane (C4H10) has two isomers
...


CH3 – CH2 – CH2 – OH
1-propanol
CH3 – CH = CH – CH3
2-butene

OH
|
CH3 – C – CH 3

2-propanol
CH3 – CH2 – CH = CH2
1-butene

(iii) Functional Isomerism : Compounds having the same molecular formula but different functional groups
are called functional isomerism
...
In common
usage, it is often referred to simply as alcohol
...

44

Carbon and its Compounds

Class X-Chemistr y

Chemical formula of ethanol
Ethanol’s hydroxyl group is able to participate in hydrogen bonding
...
Ethanol, like most
short-chain alcohols, is flammable, colourless, has a strong odour, and is volatile
...
3614, and is a versatile solvent
...
Due to the hydrogen bonding properties of ethanol, it can absorb water from the air
...
The ethanol molecule has a hydrophilic OH group
that helps it dissolve polar molecules and ionic substances
...
Thus ethanol can dissolve both polar and non-polar substances
...
During the 1990s, low petroleum prices made ethylene hydration a more economical
process than fermentation for producing ethanol
...

In an older process, first practiced on the industrial scale in 1930 by Union Carbide, but now almost entirely
obsolete, ethene was hydrated indirectly by reacting it with concentrated sulfuric acid to produce ethyl
sulfate, which was then hydrolysed to yield ethanol and regenerate the sulfuric acid:
C2H4 + H2SO4  CH3CH2SO4H
CH3CH2SO4H + H2O  CH3CH2OH + H2SO4

Fermentation
Ethanol for use in alcoholic beverages, and the vast majority of ethanol for use as fuel, is produced by
fermentation: when certain species of yeast (most importantly, Saccharomyces cerevisiae) metabolize sugar
in the absence of oxygen, they produce ethanol and carbon dioxide
...
In the presence of oxygen,
yeast undergo aerobic respiration which produces carbon dioxide and water, and does not produce ethanol
...
However, in some countries, rectified spirit (95-96%) is sold directly to the consumer, for human consumption
...
5-60%
...
In order to relieve non-beverage industries of this tax burden, governments specify formulations for
denatured alcohol, which consists of ethanol blended with various additives to render it unfit for human
consumption
...

Absolute ethanol
Absolute or anhydrous alcohol or 100% alcohol generally refers to purified ethanol, containing no more than
one percent water
...
For human consumption, currently, the most popular method of purification
past 95
...

Neutralized ethanol
Neutralized ethanol is used for some analytical purposes
...
Neutralized ethanol is used in order to compensate for this error
...
The so obtained “neutralized ethanol” is then added to
the target of the titration, which may be sample of neat organic acid
...
This way, the indicator neutralization error is eliminated
...
The largest national fuel ethanol
industries exist in Brazil (gasoline sold in Brazil contains at least 20% ethanol and hydrous ethanol is also used
as fuel)
...
For use as an additive to petrol, almost all water must be removed, otherwise
it will separate from the mixture and settle to the bottom of the fuel tank, causing the fuel pump to draw water
into the engine, which will cause the engine to stall
...
Pure, water-free acetic acid (glacial
acetic acid) is a colourless liquid that attracts water from the environment (hygroscopy), and freezes below
16
...
Acetic acid is corrosive, and its vapour causes irritation to the
eyes, a dry and burning nose, sore throat and congestion to the lungs, however, it is considered a weak acid
due to the fact that at standard temperature and pressure the dissociated acid exists in equilibrium with the
undissociated form in aqueous solutions, in contrast to strong acids, which are fully dissociated
...
It is an important chemical reagent and industrial chemical that is used in the production of polyethylene terephthalate
mainly used in soft drink bottles; cellulose acetate, mainly for photographic film; and polyvinyl acetate for
wood glue, as well as many synthetic fibres and fabrics
...
In the food industry acetic acid is used under the food additive code E260 as an acidity
regulator
...
Acetic acid is a weak, effectively monoprotic
acid in aqueous solution, with a pKa value of 4
...
Its conjugate base is acetate (CH3COO–)
...
0 M solution
(about the concentration of domestic vinegar) has a pH of 2
...
4% of the acetic acid
molecules are dissociated
...
Today, the biological route accounts
for only about 10% of world production, but it remains important for vinegar production, as many of the world
food purity laws stipulate that vinegar used in foods must be of biological origin
...

Vinegar
In the form of vinegar, acetic acid solutions (typically 5% to 18% acetic acid, with the percentage usually
calculated by mass) are used directly as a condiment, and also in the pickling of vegetables and other foodstuffs
...
The amount of acetic acid used as vinegar on a worldwide
scale is not large, but historically, this is by far the oldest and most well-known application
...
With a moderate dielectric
constant of 6
...
It readily mixes with many other polar and
non polar solvents such as water, chloroform and haxene
...

Soaps, Detergents and Cleaning
Fats are isolated from plants and animals
...

Fats are heated with a strong base to convert them into soaps
...
One typical animal fat,
stearol, reacts with KOH to form potassium stearate, a soap
...


The potassium soap formed from fat is converted to a sodium soap by replacing the potassium ions with
sodium ions
...
You may also notice that the potassium soap is softer than the sodium soap
...


48

Carbon and its Compounds

Class X-Chemistr y

Both potassium and sodium soaps dissolve in water and are effective as cleaning agents
...
The
polar end attracts polar water molecules
...
Water is a polar
solvent and dissolves polar and ionic molecules
...
A way to remember this behavior is
the simple axiom; “Like dissolves like
...
The negatively
charged groups on the surface are attracted to the
water molecules
...

A spherical structure with the polar portions of the
molecule on the surface and the nonpolar parts of the
molecule in the center is attracted to the water and
carries the non-water-soluble material away with it
...

Magnesium and calcium salts of the same fatty acids that make up potassium and sodium soaps are not
water soluble
...
To achieve the same
washing or cleaning action, more soap must be added
...
The
molecules of detergents also have polar and nonpolar ends
...
In recent years many
different detergents have been introduced for use in cleaning
...


49

Carbon and its Compounds

Class X-Chemistr y

ASSIGNMENTS
Multiple Choice Questions
1
...


3
...


(d)

(b) basic

(c) neutral

(d) can not say

(b) second

(c) third

(d) fourth

(c) Desi Ghee

(d) Cooking oil

(c) 5

(d) 8

Bromine water can be decolourised by
(b) Vanaspati Ghee

No
...


(c)

In which period of periodic table carbon is found ?

(a) 3
8
...


+ H2O is

(c) Free radical substitution reaction

(a) first
6
...


(c) Co-ordinate

(a) Electrophillic substitution reaction

(a)
4
...


50

(b) 5-hexyne-3-ene

Which of the following pairs shows isomerism ?
(a) CH4 and C2H6

(b) CHCl3 and CCl4

(c) CH3 CH2 OH and CH3OCH3

(d) NaCl and KCl

Carbon and its Compounds

Class X-Chemistr y

Fill in the blanks
1
...


2
...


3
...


4
...


5
...


True / False
1
...


2
...


3
...


4
...

|
|
Cl
Br

5
...


Subjective Questions
1
...


Write structure of pent-3-ene-1-yne
...


Explain the action of soap and detergents ?

4
...

Why?

5
...


Convert :
(i) Ethanol to ethanoic acid

(ii) Ethyl acetate from Ethanol and ethanoic acid

(iii) Ethanol to ethene

(iv) Ethanoic acid to sodium ethanoate
51

Carbon and its Compounds

Class X-Chemistr y

ANSWERS
Multiple Choice Questions :
1
...


(a)

3
...


(a)

5
...


(d)

7
...


(b)

9
...
(c)

11
...


14

2
...


aromatic

4
...


water

True / False
6
...


True

8
...


False

10
...


(3-ethyl-6-methyl octane)

2
...

Dobereiner’s triads: It was the first attempt towards classification
...

e
...
Ca40 Sr87
...
wt
...
5
2

88
...
5 of atomic weight of Sr
...
5 Br80 I127
At
...
of Br =

35
...
25
2

81
...


Newland’s law of octaves: When the lighter elements are arranged in order of their increasing atomic
weights, then every eighth element are similar to the first element in their properties, similarly as the eighth
note of a musical instrument is similar to 1st one
...
g
...
Similarly K the 8th element with Na and so on
...

Lother Meyer arrangement: According to him the elements which are similar in their chemistry
occupied similar positions on the graph of atomic volume vs atomic weights e
...
(a)
...

(b) Halogens occupy the ascending positions on the curve
...

But later on, he modified the statement after considering the Lother Meyer’s work
...

Periodic table: The table which classifies all the known elements in accordance with their properties in
such a way that the elements with similar properties are grouped together in the same group while
dissimilar elements are in the other group
...

b) Helps in the discovery of new elements
...
g
...

c) Correction of doubtful atomic mass
...

e) Correction in the position of some elements
...


ii)

Position of isotopes: Isotopes must have different positions but they are placed in the same group
...


54

Periodic Classification of Elements

Class X - Chemistr y

iv)

Dissimilar elements are placed together in the same group like K & Cu in 1st group
...


vi)

Some higher atomic weight elements placed before the lower atomic weight elements e
...
Ar40
precedes K39, Co58
...
7, Te127
...


vii)

Position of metals and non-metals: Both are placed together in the same group
...


ix)

Lanthanides and actinides were placed separately at the bottom of the periodic table
...


xi)

Position of noble elements
...


xiv)

Cause of periodicity can not be explained
...
Moreover the
atomic number of an element is its serial number or position number in the periodic table
...


Modern Periodic Law
a) The properties of elements are the periodic function of their atomic numbers
...

The Modern Periodic Table
The modern periodic table is divided horizontally into periods from left to right whereas vertically it is divided
into columns called groups
...
The first period contains 2 elements
...
These two periods are known as short periods
...
Seventh period is
incomplete
...

Let us now examine critically the relation between the electronic configuration of an element and its
position in the long form of periodic table
...
The first period : Contains two elements – H and He
...
g
...

2
...
Since
this principal quantum number can have two subshells s and p which can contain maximum of 2
and 6 electrons respectively, the total number of elements in the second period is 8
...
Hence 8 elements are there in the second period
...
The third period : The principal quantum number of the third period is three (n = 3)
...

4
...
It begins
with K (1s2 2s2 2p6 3s2 3p6 4s1) and ends with Kr (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6)
...

5
...
It begins with Rb
and ends with Xe
...
It is the second long period which contains 18 electrons
...
The sixth period : The principal quantum number of sixth period is six (n = 6)
...

7
...
This
period is repetition of the sixth period having 19 elements so far discovered
...


Type – 1 – Inert gas elements : Elements with outermost shell electronic configuration ns2np6
[except He (1s2)] are called inert gas elements
...
Because of the stability of their electronic
configurations, these elements do not enter into ordinary chemical reactions
...


2
...
Elements of Groups 1, 2, 13, 14, 15, 16 and 17 are the members of this
class
...
They tend to enter into chemical combination
either by sharing or losing or gaining electrons to attain the electronic configuration ns2 np6 for the
outermost shell
...


3
...
These elements are also called dblock elements
...
The
series begins with Group 3 elements Sc, Y, La and Ac and ends with Cu, Ag, Au and Ha (105)
(incomplete)
...


4
...
e
...
As a result (n – 2)f subshell is progressively filled
...
(n – 1) s2p6d0 or 1
ns2
...
They are
trivalent having similar chemical properties
...


Classification of elements into s, p, d and f blocks
1
...
Thus the last electron enters the ns orbital and as a result, these elements have
either ns1 or ns2 configurations in the ground state
...
s-block elements are placed at the extreme left in the periodic table
...


p-block elements : In the atoms of p-block elements, the last electron enters the p-orbital of the
outermost shell
...


3
...
e
...
As the (n – 1)d orbital of these elements is
progressively filled they are called d-block elements
...
They occupy the middle of the periodic
table between s and p-block elements
...


f-block elements : Elements having the general electronic configuration of valence shell
(n – 2)f1–14(n – 1)s2 p6 d1 or 0 ns2 are called f-block elements
...
Hence the name f-block elements
...


Characteristics of Periodic Table
Periodicity of properties of elements : According to the modern periodic law, the properties of elements
are periodic functions of their atomic numbers
...

i)

Density : It is observed that the density increases from left, then reaches a maximum in the central
position and then decreases with the rise of atomic number
...


ii)

Atomic radius or atomic size : Atomic radius is defined as the distance between the centre of the
nucleus and the outermost shell of the atom
...

Explanation : As we move from left to right across a period, the atomic number increases with the
increase in the positive charge on the nucleus, but the outer electron shell remains same resulting in
increase in attraction and thus a decrease in the atomic radius
...

The abrupt increase in atomic radius of 18 group elements is due to the fact that the radius of the
noble gases are not covalent radii but are Vander Waal’s radii
...


Explanation : The increase of atomic radius from top to bottom is due to the addition of new
quantum shell, as a result the distance between the nucleus and the outermost electron increases
...

In a period : Thus, as we move from left to right across a period, the metallic character of an
element decreases and non-metallic character increases
...

57

Periodic Classification of Elements

iv)

Class X - Chemistr y

Ionisation potential: The first ionisation potential of an element is defined as the amount of energy
necessary to remove the outermost electron i
...
, most loosely bound one, from its isolated gaseous
atom in its lowest energy state, against the force of attraction existing between the nucleus and that
electron, so as to give a cation, in the gaseous state
...
This is attributed to the
decreased atomic radius coupled with increased effective nuclear charge as a result of which the
force of attraction between the nucleus and the outermost electron increases
...

Variation along a group: As we move down a group the ionisation potential normally decreases
...


v)

Electron Affinity: The electron affinity of an atom is the amount of energy released by an isolated
neutral gaseous atom in its ground state (lowest energy state), when it captures an electron to form
a uni negative ion
...
This is due to the decrease of atomic radius coupled with increased effective
nuclear charge
...

Variation along a group: As we move from top to bottom in a group, the electron affinity decreases
which is due to their increased size
...


vi)

Electronegativity: According to Linus Pauling, electro-negativity of an atom in a molecule is defined
as its relative power to attract the shared electron pair in a covalent bond towards itself
...

Variation in a group: In a group as we go down, electronegativity decreases
...
Though the effective nuclear charge increases, the increase of atomic
radius outweights this effect
...


Elements belonging of the same group have similar properties because
(a) they have similar electronic configuration of the outermost shell
(b) their atomic numbers go on increasing as we move down the group
(c) all of them are metallic elements
(d) none of the above

2
...


58

(c) Ca, Cl

Periodic Classification of Elements

Class X - Chemistr y

4
...


Element having the highest electron affinity is
(a) Br
(b) Cl

(c) I

(d) F

6
...


Mark the group which has maximum number of elements in Mendeleeff’s periodic table
(a) I
(b) II
(c) III
(d) IV

8
...
of elements in fifth period of periodic table is
(a) 8
(b) 32
(c) 18

(d) 19

The most electronegative element is
(a) nitrogen
(b) fluorine

(d) chlorine

9
...


The energy released when electron is added to a neutral gaseous atom is called ____________ of
the atom
...


Inert gases have ____________ radii hence there is a sudden increase in atomic radii as we move
to end of a period
...


The amount of energy required to remove the most loosely bound electron from an atom is called its
____________
...


Atomic radius ____________ from top to bottom in a group
...


Ionisation potential ____________ on going down a group
...


The energy is released when a cation is formed from neutral atom
...


All transition elements are metals
...


Metallic character increases in moving down a group from top to bottom
...


The electron affinity of fluorine is highest among halogens
...


The ionisation potential of Mg is larger than Na
...


In a period, the size of the atom decreases with the increase of atomic number but at the end of each
period, in the noble gas, the atomic size increases abruptly
...


Potassium is more electropositive than sodium

3
...


4
...

59

Periodic Classification of Elements

Class X - Chemistr y

5
...
8) has a lower ionisation energy than that of nitrogen (at no
...


s-block elements are very reactive
...


Noble gases have zero electrons affinity
...


Arrange the following in increasing order of the property indicated i)

F, Cl, Br and I (electron affinity)

ii) Mg, Al, Si and Na (Ionisation potential)
iii) F, Cl, Br and I (electronegativity)

ANSWERS
Multiple Choice Questions :
1
...


(b)

3
...


(c)

6
...


(c)

8
...


(b)

Fill in the blanks :
1
...
vander waal’s
3
...
increases
5
...
False
2
...
True
4
...
True

Subjective Type Questions
8
...
I < Br < F < Cl
2
...
I < Br < Cl < F


60

5
...
Some of them are slow and some are fast
...
g
...
The rusting of iron takes days or months to take place and is a very slow process
...
But
the rate of reaction can be altered to suit our requirement
...
For
example, the hydrogenation of oil into fat takes place in the presence of Ni or Pt as a catalyst
...

The rate of reaction tells how fast the reaction is taking place by indicating how much of a reactant is
consumed, or how much of a product is formed in a given time
...

Types of Rate of Reactions
Rates of reaction are of two types :
i)

Average reaction rate : It is defined as the total change in concentration of reactant
...


Average rate of formation of B =
ii)

[B]
t

Instantaneous reaction rate : It is for a short interval of time and for a very small change in
concentration of reactant or product
...
The concentration of A
decreases with time and concentration of B increases with time
...

Generally, for a reaction,
aA + bB  cC + dD

1 [A]
1 [B]
1 [C]
1 [D]



a t
b t
c t
d t
The reaction rate is defined as the rate of decrease of concentration of a reactant, or the rate of increase of
concentration of product, and is always given as a positive number
...

(i)

The chemical reactions in which the heat is released are called exothermic reactions
...
g
...


(ii) The chemical reactions in which the heat is absorbed are called endothermic reactions
...
g
...


Effect of concentration on the rate of reaction
The chemical reaction takes place as a result of the collision between the reactant molecules when the
reactants come into contact with each other
...
The chances of such collisions increase with increase in concentration of the reacting
substances
...

e
...
,

2NO (g) + O2(g) 

2NO2(g)

the rate of reaction doubles when we double the concentration of oxygen and quadruples (four times) when
we double the concentration of NO
...
e
...
Some reactions are catalysted by external
agent while others do not have such influence
...

In the present chapter our main objective is to answer “how far” a chemical reaction proceeds, whether a
reaction is complete or incomplete and the influence of environment i
...
, temperature, pressure, concentration
etc
...


Concept of reversible reaction
When an aqueous solution of sodium carbonate is added to an aqueous solution of calcium chloride immediately
white CaCO3 is precipitated out
...

62

Rate of Chemical Reactions and Chemical Equilibrium

Class X - Chemistr y

In the above reaction Na has a strong affinity towards Cl atom; similarly Ca atom has strong affinity towards
CO3 radical
...
Consequently this pair will not combine to reform
sodium carbonate and calcium chloride
...
e
...

Large deposit of TRONA (Na2CO3) are found on the banks of certain saline lakes in Egypt
...
L
...

2NaCl + CaCO3 = CaCl2 + Na2CO3
Hence the reverse reaction also takes place depending on the environment i
...
, concentration
...
”

Definition : A reaction is said to be reversible when the reactants combine among themselves to form the
products which as soon as formed, start reacting among themselves to reform the reactants and attain a state
of equilibrium depending upon the concentration and other conditions of the components of reaction
...


Chemical equilibrium
When an equimolecular mixture of hydrogen and iodine is heated at 440ºC in a closed vessel for about two
hours or so, 80% hydrogen iodide is formed
...

Now in a similar closed vessel pure HI is kept at 440ºC
...

H2 + I2 ƒ 2HI
Initially the concentration of H2 and I2 was maximum with time the forward reaction proceeds but the
concentration of HI remains comparatively low, which indicates a reversible reaction
...
As time is elapsed, the
concentration of H2 and I2 decreases and the concentration of HI is increased
...
The process continues and the
decrease of the rate of the forward reaction and the increase of the rate of the backward reaction reaches
a point when the speed of the forward reaction becomes equal to the speed of the backward reaction
...


Definition : Chemical equilibrium is defined as a state when the velocity or speed of the forward reaction is
the same as the velocity or speed of the backward reaction of a reversible reaction
...

(a) The rates of forward and backward reaction are the same and the two reactions act in opposite direction
...
Thus it
appears as if the reaction has been stopped
...

Hence there is change of point of chemical equilibrium
...
e
...


Laws of mass action
The effect of the concentration of the reactants on the rate of a chemical reaction is governed by the Law of
mass action which was put forward in 1867 by C
...
Guldberg and P
...
The Law states :
The rate of a chemical reaction at any instant at a given temperature is proportional to the active mass of
each of the reacting substances present in the system at that instant
...


Active mass : By the term active mass we generally mean the molar concentration of the reactant i
...
,
gram-moles per litre or moles per litre
...

[NaOH] =

20
= 0
...

(i)

In gaseous system the concentration of the gas is expressed in term of their partial pressures since
partial pressure of a gas per unit volume is proportional to its moles
...


Equilibrium constant
The expression of equilibrium constant for a general equation of the type
...
In other words, it is the ratio of concentration of the products and the reactants, each
being raised to a power indicating the number of moles of the substances taking part in the reaction
...
g
...


(i)

Kc : When the reaction is considered in aqueous medium and the concentrations of the reactants
and the products are expressed in moles per litre, the equilibrium constant (K) is written as Kc

[C]c [D]d
Kc =
[A]a [B]b
(ii) Kp : When we consider a gaseous reaction the equilibrium constant is replaced by Kp
...
In that case the expression for equilibrium
constant is
64

Rate of Chemical Reactions and Chemical Equilibrium

Kp =

Class X - Chemistr y

[PC ]c  [PD ]d
[PA ]a  [PB ]b

Where PA, PB, PC and PD are the partial pressures of the gaseous components A, B, C and D respectively
...


[C]c [D]d
Kc =
[A]a [B]b
Again let PA, PB, PC and PD be the partial pressures of the gaseous component A, B, C and D respectively
...

V

Substituting for the components A, B, C and D,
PA = [A]RT,

PB = [B]RT,

PC = [C]RT,

PD = [D]RT

Substituting the aboves values of PA, PB, PC and PD in the expression for KP

[C]c [RT]c [D]d [RT]d
KP =
[A]a [RT]a [B]b [RT]b

KP =

[C]c [D]d [RT]c [RT]d

...

65

Rate of Chemical Reactions & Chemical Equilibrium

(i) When n = 0

Kp = Kc [RT]0

or,

Class X - Chemistr y

Kp = Kc

Examples :
H2

 I2

(g )
1 mole

ƒ

2HI

(g)
2 moles

(g)
1 mole

(PHI ) 2
[HI]2 [RT]2
[HI]2


Kp = (P )
...
(P ) 3  [N ][H ] 3 [RT]4  [N ][H ]3
...


Types of chemical equilibrium
Two types of chemical equilibria are known
...

Example :

2SO2(g) + O2(g) ƒ
CH3COOH

(l)

+ C2H5OH

(l)

ƒ

2SO3(g)
CH3COOC2H5 (l) + H2O(l)

(b) Heterogeneous equilibrium : A system is said to a Heterogeneous one, if the phase of any one
component is different from the other
...

Example :

C(s) + O2(g) ƒ
CaCO3(s) ƒ

CO2(g)
CaO (s) + CO2(g)

Law of mass action is applicable to both homogeneous and heterogeneous equilibria
...


i)

Concentration: When the concentration of any of the reactants or products in a reaction at equilibrium
is changed, the composition of the equilibrium mixture changes so as to minimize the effect of concentration
change
...
g
...

66

Rate of Chemical Reactions and Chemical Equilibrium

Class X - Chemistr y

ii) Pressure: The effect of pressure change is important in a reaction involving gases
...

The increase in pressure shifts the equilibrium in a direction which yields less number of gaseous moles
and decrease in pressure favours the direction which yields more number of moles
...
g
...

CO(g) + 3H2(g) ‡ˆ ˆˆ †ˆ CH4(g) + H2O(g)

In this reaction

n = (1 + 1) – (1 + 3) = – 2
The increase in pressure shifts the equilibrium in the forward direction
...


iii) Temperature: Temperature affects a reaction in two ways :
(i)

It increases the rate (speed) of the reaction and helps the reaction to attain equilibrium at a fast
rate
...

The way temperature affects Kc or Kp depends on enthalpy change, Hº for the reaction
...

In exothermic reaction, (Hº = –ve), the increase in temperature shifts the equilibrium to left and
decrease in temperature shifts the equilibrium to right
...


iv) Catalyst: Catalyst is a substance which speed up the reaction and is recovered chemically unchanged
at the end of the reaction
...
It increases the rate of forward and the backward
reactions by he same factor and helps the reaction to attain equilibrium at a faster rate
...

67

Rate of Chemical Reactions & Chemical Equilibrium

Class X - Chemistr y

ASSIGNMENTS
Multiple Choice Questions
1
...


For the reaction A + 2B  3C, the rate equation is
(a)

 d [A]  d [B]

dt
dt

(c) 

1 d [B]
1 d [C]

2 dt
3 dt

(b)

 d [A]  d [C]

dt
dt

(d) 

1 d [B]
3d [C]

2 dt
dt

3
...


The correct expression for the equilibrium constant for the reaction
1
3
NH3(g) ‡ˆ ˆˆ †ˆ
N2(g) + H2(g); is
2
2

5
...


The value of Kc _______________ with the change of temperature
...


Law of mass action states that the rate at which a substance reacts is proportional to its
_______________
...


For a gaseous reaction
2A ‡ˆ ˆˆ †ˆ B
the eq
...


4
...


Rate of Chemical Reactions and Chemical Equilibrium

5
...


True / False
1
...


2
...


3
...


4
...


Kc = Kp/RT

For the reaction,
PCl5 ‡ˆ ˆˆ †ˆ PCl3 + Cl2
dissociation of PCl5 increases with increase in pressure
...


The reaction 3Fe + 4H2O ‡ˆ ˆˆ †ˆ Fe3 O4 + 4H2, behaves a reversible reaction in a closed vessel, but
not in an open vessel
...


The numerical value of the equilibrium constant Kc changes with the change of temprature
...


A chemical equilibrium is a dynamic one, not static
...


If concentration are expressed in moles L–1 and pressure in atmospheres, what is the ratio of Kp to
Kc for the reaction
...


2SO3(g) at 25ºC ?

At certain temperature KC is 16 for the reaction
SO2 (g) + NO2 (g)

SO3 (g) + NO (g)

If we take one mole each of all the four gases in a one litre container, what would be the concentration
of NO2 at equilibrium?
69

Rate of Chemical Reactions & Chemical Equilibrium

Class X - Chemistr y

ANSWERS
Multiple Choice Questions
1
...
(c)

3
...
(a)

Fill in the blanks :
(i)

changes

(ii) concentration
(iii) KC/RT
(iv) remains constant
(v) 1/7
True / False
(i)

False

(ii) False
(iii) True
(iv) True
(v) False

Subjective Type Questions
4
...
04
...


0
...




70

5
...

Thus if  mole ionises out of one mole of the dissolved electrolyte, the degree of ionisation is 
...
“The degree of ionisation is ”, means
that out of every mole of the electrolyte  mole ionises and (1 – ) mole is left unionised in the solution
...
It further states that, at a constant
temperature, a weak electrolyte in solution gets more ionised with the increase of dilution
...
(1)

or

A–
 gm-ion
C  gm-ion


gm-ion per litre
V

Applying law of mass action,

If M A is a weak acid, K is called ionisation or dissociation constant of the acid and is symbolised as Ka
...

Now putting the values in terms of concentrations (1),
Cα × Cα C 2

K=
C (1 – ) 1 – 
If  is small in comparison to 1 i
...
, for a weak electrolyte the dissociation is very small
...
(2)
71

Ionic Equilibria

Class X - Chemistr y

 

2
Again,
K= V V 
as (1 – )  1; K = 2/V or,
 = K
...
(3)
1 –  (1  )V
V
Both the equations (2) and (3) are mathematical expression for the Ostwald’s dilution law
...
(2) it is evident that the degree of ionisation () must increase with the decrease of
concentration
...
Hence at infinite dilution a weak electrolyte behaves like a strong electrolyte
...
e
...


Ionic product of water (KW)
Kohlrausch and Heydweiller showed from the conductance measurement that pure water may be regarded
as a very weak electrolyte dissociating as
H 2O



H+

+

OH–

Applying law of mass action,
[H  ][OH – ]
K=
[H 2 O]
K is called the ionisation constant of water
...
[OH–]
The product of ionic concentration [H+]
...
Kw is called ionic
product of water, because it is equal to the product of the ionic concentration of the H+ and OH– ions of
water
...
At 298 K the value of
Kw = 1
...
With the rise of temperature the value of Kw increases
...
05×10–14

1
...
89×10–14

3
...
8×10–14

pH and pOH
pH and pOH are the two scales of expressing the concentrations of H+ and OH– ions respectively in dilute
solution
...
/litre
...
According to him,
pH = log

1
,
[H + ]

or pH = –log [H+] or, [H+] = 10–pH

Thus pH is the negative logarithm to the base 10 of the hydrogen ion concentration in the solution
...
These solutions have pH
72

Ionic Equilibria

Class X - Chemistr y

between 0 and 14 and so it is more convenient to express the acidity in terms of pH rather than [H+]
...

(i)

Neutral solution has pH = 7, pure water has pH = 7
...


(iii)

An alkaline solution has pH greater than 7
...
A neutral
solution is one in which [H+] = [OH–]
...

pOH

=

[OH – ] =

or

– log [OH–]
10 –pOH

We know, [H+] [OH–] = Kw = 1 × 10–14
Taking log on both sides,
log [H+] + log [OH–] = log Kw = log (1 × 10–14)
or

– log [H+] – log [OH–] = – log Kw = – log (1 × 10–14)

or

pH + pOH = pKw = 14

In a neutral solution pH = pOH = 7
i
...
, [H+] = [OH–] = 1 × 10–7 gram-ion/litre
...
They retain practically a constant pH value
...
It consists of either a mixture of
weak acid and its salt with strong base or a weak base and its salt with strong acid
...


pH of buffer solution
The pH of a buffer solution is calculated by applying Henderson’s equation
...

HA
Ka =



H+ + A–

[H + ][A – ]
or
[HA]

[H+] =

K a [HA]
[A – ]
73

Ionic Equilibria

Class X - Chemistr y

Taking log on both sides,
log [H+] = log Ka + log

[HA]
[A – ]

or

– log [H+] = – log Ka – log

or

pH = pKa + log

i
...
, pH = pKa + log

[HA]
[A – ]

[A – ]
HA

[Salt]
This is called Henderson’s equation
...

Similarly in case of mixture of weak base and its salt with strong acid, the form of Henderson’s equation is pOH = pKb + log

[Salt]
[Base]

Application of Buffers
(i)

In biochemistry : Blood and various other human fluids are highly buffered with bicarbonate,
carbonic acid and proteins
...
4 – slightly alkaline
...
7, the result may be fatal
...
g
...


ASSIGNMENTS
Multiple Choice Questions
1
...
1 M CH3COOH (weak electrolyte) is
(a) 1
(c) less than one

(b) zero
(d) more than one

2
...
5, 3
...
5 respectively
...


The units of Kw are
(a) mol L–1
(c) mol2 L–2

4
...


Class X - Chemistr y

In a Buffer solution the ratio of salt to acid is increased ten times
...


The Kw for water at 298 K is _____________
...


Lower is the pKb ______________ will be the base
...


Degree of ionisation decreases with increase in ____________
...


The reaction between an acid and base is called _________________
...


Ka × Kb = ____________
...


pKw = log Kw
...


With decrease in pH acidic character increases
...


pH of 10–8 M KOH is 6
...


Vinegar is acidic in nature
...


pH of 10–8 HCl is very close to 7
...


At 90ºC pure water has [H+] = 10–6 M
...
?

2
...
5 M HF solution (Ka = 2 × 10–4) ?

3
...


Predict the pH of a solution obtained by mixing 0
...
1 M HA (Ka = 1 × 10–6) ?

5
...
Explain why ?

ANSWERS
Multiple Choice Questions
1
...

Fill in the blanks
1
...

5
...
False
5
...
10–12

(c)

3
...


(c)

5
...
stronger

3
...


2
...
False

4
...
2

3
...
6

(d)

neutralisation



75

Contents
SECTION I
Chapter 1

Chemical Reactions & Equations
...
09 – 18

Chapter 3

Metals and Non-Metals
...
31 – 52

Chapter 5

Periodic Classification of Elements
...
61 – 70
and Chemical Equilibria

Chapter 2

Ionic Equilibria

---