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CHAPTER – 2

ACIDS, BASES AND SALTS
q

Acids
– Sour in taste

– Bitter in taste

– Change the blue litmus to red

– Change red litmus to blue

– eg
...
Sodium hydroxide NaOH

– SulphuricAcid H2SO4

Potassium hydroxide KOH

– Nitric Acid HNO3

Calcium hydroxide Ca(OH)2

– Acetic Acid CH3 COOH
q

Bases

– Ammonium hydroxide NH4OH

Some Naturally occuring acids
Vinegar

–

Acetic Acid

Orange

–

Citric Acid

Lemon

–

Citric Acid

Tamarind

–

Tartaric Acid

Tomato

–

Oxalic Acid

Sour milk (Curd)

–

Lactic Acid

Ant and Nettle sting

–

Methanoic Acid

q

Acid – Base Indicators – Indicate the presence of an acid or base in a
solution
...
It is a purple day extracted from
Lichens
...


q

Olfactory indicators – Show odour changes in acidic or basic media
...

onion and clove
...
No
...


Blue litmus solution

To red

No change

B
...


Turmeric

No change

To red

D
...


Phenolphthalein (colourless)

No change

To pink

q

Dilute Acid : Contains only a small amounts of acid and a large amount of
water
...


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Chemical Properties of Acids and Bases
→
Acid + Metal  Salt + Hydrogen

(Refer activity 2
...
19 of NCERT Book)
→
2HCl + Zn  ZnCl2 + H2
→
2HNO3 + Zn  Zn (NO3)2 + H2

→
H2SO4 + Zn  ZnSO4 + H2
→
2CH3COOH + Zn  (CH3COO)2 Zn + H2
q

Pop test : When a buring candle is brought near a test tube containing
hydrogen gas it burns with a ‘Pop’ sound
...


q

→
Base + Metal  Salt + Hydrogen
→
NaOH + Zn  Na2ZnO2 + H2

Sodium Zincate
Note – Such reactions are not possible with all the metals
...

q

Reactions of metal oxides with acids
→
Metal Oxide + Acid  Salt + Water

+

Copperoxide

→
HCl 

CuCl2

Hydrochloric

Copper + Water

acid

CuO

chloride

+

H2O

Note : Appearance of blue green colour of the solution because of formation
of CuCl2
...

q

Reaction of Non Metallic Oxide with Base
→
Non metallic oxide + Base  Salt + Water
→
Ca(OH)2 + CO2  CaCO3 + H2O
13

X – Science

AK

Note : Non Metallic oxides are said to be acidic in nature because on reacting
with a base they produce Salt and Water
...
3 on page 22 of NCERT Book
– Glowing of bulb indicates that there is a flow of electric current through the
solution
...

–

H+ion cannot exist alone
...

→
H+ + H2O  H3O+

–

Bases provide (OH–) ions in the presence of water

H2O
NaOH(s)  Na+(aq) + OH–
(aq)
→
H2O
KOH(s)  K+(aq) + OH–(aq)
→
H2O
Mg(OH)2(s)  Mg2+(aq) + 2OH–(aq)
→
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Alkalis
All bases donot dissolve in water
...

Common alkalis are
NaOH

Sodium hydroxide

KOH

Potassium hydroxide

Ca(OH)2

Calcium hydroxide

NH4OH : Ammonium hydroxide
Note : All alkalis are bases but all bases are not alkalis
...
The acid must
always be added to water with constant stirring as it is highly exothermic
reaction
...
This results
in the decrease in the concentration of H3O+ or OH– per unit volume in acids
and bases respectively
...
of H+ions and OH–ions
produced respectively
...
This indicator is called PH scale
...

This scale measures from 0 (very acidic) to 14 (very alkaline) 7 Neutral
(water in Neutral)
...

Variation of PH
S
...
Value

Colour of the
pH Paper

Nature of
Solution

H+ion
Conc
...


1
...


4

Orange or yellow

Acidic

high

low

3
...


10

Bluish green or blue

Alkaline

low

high

5
...

eg
...


–

Weak Acids give rise to less H+ ions
eg
...

eg
...

eg
...
No
...


Potassium Sulphate

K2 SO4

KOH

H2SO4

2
...


Sodium Chloride

NaCl

NaOH

HCl

4
...
Similarly NaCl and KCl belong to the family of chloride
salts
...
In case of indigestion our stomach produces acid in a
very large quantity because of which we feel pain and irritation in our stomach
...
These antacids neutralises the
excess acid and we get relief
...
6 it is called Acid
Rain
...


q

pH of Soil : Plants require a specific range of pH for their healthy growth
...


q

Our body functions between the range of 7
...
8 living organisms can
survive only in the narrow range of pH change
...
Using toothpaste
which is generally basic can neutralise the excess acid and prevent tooth
decay
...
When we use a weak base like baking soda on it we get relief
...
NaCl, CaSO4
Acidic Salts : Strong Acid + weak base
pH value is less than 7
eq
...
CaCO3, CH3 COONa
q

Chemicals from Common Salt
– Sodium chloride is called as common salt used in our food
...

– Rock Salt is the brown coloured large crystals
...

– Common Salt is an important raw material for many materials of daily use
such as
...


q

Sodium Hydroxide
Preparation : Prepared by the method called chlor-alkali
Called chlor-alkali because we get chlorine and a base in this
...

Uses :

In household, ingredients of antacid
In making baking power

On heating baking powder produces
→
NaHCO3 + H+  CO2 + H2O + Sodium Salt of acid
q

Washing Soda
Preparation : Recrystallisation of sodium carbonate
Na2CO3 + 10H2O
Uses
–
–
–
–

q

Heat →


Na2CO3
...

Removal of hardness of water
...


Water of crystallisation : Fixed no
...

–

On heating copper sulphate crystals water droplets appear, formula of
hydrated copper sulphate – CuSO4
...

18

X – Science

AK

–

gypsum also contains water of crystallisation
...
2H2O

–

On heating gypsum at 373k it becomes CaSO4
...


–

Plaster of Paris is used as plaster for fractured bones
...

→
CaSO4
...
2H2O

Uses of plaster of Paris : Making toys, decorative material and smooth surfaces
...


Two solution have pH number 4 and 9 respectively which solution has more
H+ ion concentration?

2
...


What is the chemical name of bleaching powder?

4
...


5
...


Name the gas evolved when dil
...


7
...


What do you observe when a buring candle is brought near the testube
containing hydrogen gas?

9
...


10
...


Short Answer Type Questions

(2 marks)

1
...


→
Complete the reaction CaCO3 + H2O  name the products formed
...


A testtube contains solution of NaOH and Phenolphthalein
...


4
...


In a beakey a solution of HCl is poured and an electric circuit containing bulb
is placed systemtically
...


Identify the type of reaction
→
H X + M OH  MX + HOH
Why all bases are not alkalies but all alkalis are bases?

Answer the following questions in detail

(3 marks)

1
...


What happens when a metal react with dilute hydrochloric acid? Write the
reaction
→
© NaOH + Zn  _________ + _________
...


What happens when an acid or a base is added to the water? Why does the
beaker appear warm? Why should we always add acid or base to the water
and not water to the acid or base
...


(5 marks)

Write down five products formed with the help of common salt on
industrial level
...


(a)

Write down the chemical name of these compounds and one use of
each of them
...


...

→

d)

NaOH

e)

→
Na2CO3 + 10H2O  _______

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