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Title: Basic concepts
Description: Basic concepts of chemistry with long answers, short answers, and M.C.Qs.
Description: Basic concepts of chemistry with long answers, short answers, and M.C.Qs.
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1st year chemistry notes
Chapter No
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1
om
Short Question With Answer
Calculate the grams atoms in 0
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Gram atoms of potassium =
=
= 0
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2
e
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of atoms in them
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Mass of sodium = 23 gms= 1mole=6
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02x 1023 atoms
Both the substances have equal number of atoms because they have same
no
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Mg atom is twice heavier than that of carbon
...
ww
w
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3
The atomic mass of Mg is 24 which is to twice as mass as compared to the
atomic mass of carbon i
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12
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Q
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Ans
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allonlinefree
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e
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02 x 1023
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02x1023molecules
=24NAatoms
Mass of Sucrose (C12H22O11)=342g=1mole=6
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5
om
=45NAatoms
4
...
c
number of positive and negative ions, but the number of positively charged
ions are twice the number of negatively charged ions
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→ 2H+ + SO4-2
line
When one mole of H2SO4 ionizes, it produces 2H+ and
SO4–2 ions
...
Hydrogen ions are twice in number than that of SO ion
...
Similarly ions produced by
complete ionization of 4
...
a
and –ve charges but the number of H+ ions are twice than number of
negatively charged sulphate ions
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6
One mg of K2CrO4 has thrice the number of ions than the number
of molecules when ionized in excess of water
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K2CrO4
→
2K+ +
CrO4–2
When K2CrO4 ionizes in water, its one molecule gives three ions i
...
two
K+ and one CrO4–2 (chromate) ions
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1st year chemistry notes
Q
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414 dm3 at STP, although the sizes and
masses of molecules of three gases are very different from each other
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One mole of gas at STP occupies a volume of 22
...
Normally it is known
that in the gaseous state, the distance between the molecules is 300 times
e
...
Therefore two grams of H2, 16 grams of
CH4 and 44 grams of CO2 (1 mole of each gas) separately occupy a
fre
volume of 22
...
This is called molar volume
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8
line
1mole=22
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ww
w
...
Q
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/Many chemical reactions
taking place in our surroundings involve limiting reactants give examples?
Ans
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In our surrounding
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1st year chemistry notes
many chemical reactions take place which involve limiting reactants some
of these reactions are:
(i)
Burning of coal to form CO2---Coal is limiting reactatnt C +
O2 ® CO2
(ii)
Burning of sui gas to form CO2 and H2O
(iii)
om
CH4 + 2O2 ® CO2 + 2H2O
Rusting of iron----iron is limiting reactant
e
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So other reactants are limiting reactants
...
10
ten moles of electron and twenty–eight moles the total fundamental
line
particles present in it
...
llon
One molecule of H–O–H has two bounds between hydrogen and
oxygen
...
e
...
a
of bonds and three moles of atoms
(2 moles of H atoms and one mole of O atoms)
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There are 28 moles of all
fundamental particles in one mole of water i
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10 moles of electrons
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1st year chemistry notes
8 moles of neurons (8 neutrons in oxygen and there is no neutron in
hydrogen) 28 moles of fundamental particles
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11
One mole of H2SO4 should completely react with two moles of
NaOH
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H2SO4 + 2NaOH ® Na2SO4 + H2O
e
...
It needs two moles of OH ions for complete
llon
neutralization
...
One mole of H2SO4 releases
twice the Avogadro’s number of H+ ions and it will need the Avogadro’s
Q
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ww
w
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N2 and CO have same number of electrons, protons and neutrons
...
For N2 No
...
of protons in N2 = 7 + 7 = 14
No
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of electrons in O = 8
Total no
...
of neutrons in C = 6
No
...
of neutrons = 6 + 8 = 14
How many molecule, of water are in 12 gram of ice?
om
Q
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0 gm
Molar mass of water = 18 g/mol
fre
No
...
c
Ans
...
of molecules of water
= 0
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02 x 1023
llon
= 3
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14
Differentiate between limiting and non–limiting reactant ?
Ans
...
a
A limiting reactant is a reactant and that controls the amount of the
product formed in a chemical reaction
...
Q
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Actual Yield:
The amount of the products obtained in a chemical reaction is
called actual yield based on experiment
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Q
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The yield which is obtained by dividing actual yield with theoretical
om
yield and multiplying by 100 is called percent yield
...
c
Significance:
% yield indicates the efficiency of reaction
...
fre
(i)
Q
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Side reaction may takes place
(c)
llon
(b) All the reactant may not be converted into products
Mecahanical loss may occur like during
e
...
Calculate the mass of 10–3 moles of MgSO4
...
ww
w
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18
MgSO4 is an ionic compound
...
Number of moles of substance
=
Formula mass of MgSO4 = 120 gm/ml
Number of moles of MgSO4 = 10–3 moles
Applying formula
10–3 =
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1st year chemistry notes
Mass of MgSO4 = 120 x 10–3 = 0
...
19
Define Avogadro’s number ?
Ans
...
It is equal to 6
...
Define mole ?
e
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20
Ans
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1 mole of water = 18
...
21
Define isotopes ?
Ans
...
0 g
ww
w
...
For example carbon has three
isotopes
...
Similarly hydrogen has three isotopes H H H called protium, deuterium
and tritium
...
22
Define (i) ions
Ans
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Ion
As specie having positive or negative charges are called ions
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1st year chemistry notes
Positive Ion (Cation):
A specie has +ve charge is called positive ion and attracted towards
Cathode
...
Negative Ion (Anion)
A specie which has negative charge is called negative ion and
om
attracted towards anode
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23
e
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Define and explain the molecular ion ?
fre
Ans
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line
formed
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Cationic molecular, ions are more
llon
The molecular ions find applications of in calculation of molecular
mass of a compound
...
ww
w
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Q
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What do understand by the relative atomic mass ?
Relative atomic mass is the mass of an atom of element as
compared to the mass of an atom of carbon taken as 12
...
It is th of the mass of one carbon atom
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00 amu
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0078 amu
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25
Define Gram atom ?
Ans
...
om
Number of gram atoms of a meter an element
=
e
...
008 gm
1 gram atom of carbon = 12
...
line
Q
...
Number of gram ions =
1 gram ion of OH–1 = 17 grams
ww
w
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27
Define gram formula and moles ?
Ans
...
Number of gram formula or moles of a substance
=
1 gram formula of NaCl = 58
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Q
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The volume occupied by one mole of an ideal gas at standard
equal to 22
...
Q
...
e
...
The volume is
The number of atoms present in a molecule is called the atomicity
...
If the
molecule contains one atom it is monoatomic, if it contains two atoms it is
llon
diatomic, and if it contains three atoms it is triatomic
...
For example He, Cl2,
O3, P4, S8
...
ww
w
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Q
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Atom:
Atom is now defined as the smallest particle of an element, which
may or may not have independent existence
...
While atoms of hydrogen, nitrogen and
oxygen do not exist independently
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For example N2, O2, Cl2,
HCl, NH3 and H2SO4 are examples of molecules
...
31
What do you mean by empirical formula and molecular formula?
How they are related to each other ?
Empirical Formula:
om
Ans
...
e
...
Molecular Formula:
line
The formula of a substance which is based on the actual molecule
is called molecular formula
...
For example molecular formula of benzene is C6H6, while
that of glucose is C6H12O6
...
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Q
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There are many compounds, whose empirical formulas and
molecular formulas are the same
...
Their simple
multiple n is unity
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1st year chemistry notes
n =
Q
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It has 38
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7% hydrogen and 51
...
Its molar mass is 62 gms
mole–1
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H = 9
...
6%
om
C = 38
...
e
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225
fre
H = = 9
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225
line
Dividing above molar ratio by least ratio we get atomic ratio
...
a
Molar mass = 62
Empirical formula mass = 12 + 3 + 16 = 31
Now
n =
=
= 2
Molar formula = n x Empirical formula
= 2 x CH3O
Molecular formula = C2H6O2
Hence molecular formula of Ethylene glycol = C2H6O2
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1st year chemistry notes
Q
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44% carbon 5
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06% of oxygen
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15
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Ans
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of gram atoms of carbon =
e
...
om
First of all divide the percentage of each element by its atomic mass
= 5
...
of gram atoms of hydrogen =
= 5
...
of gram atoms of oxygen =
C
: H:
4
...
82 gram atoms of 0
Mole ratio
5
...
82
Divide number of grams atoms by the smallest number
H:
O
3:
1
ww
w
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So the empirical formula is C3H3O
...
Empirical formula mass
=
3 x 12 + 3 x 1 + 16
= 36 + 3 + 16 = 55
...
15
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1st year chemistry notes
h = = = 2
Molecular formula = n x empirical formula
= 2 x C3H3O
= C6H6O2
Q
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There are three useful relationships ?
Ans
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Number of molecules of a compound
e
...
3
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36
line
NA is the Avogadro’s number
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02 x 1023
...
There are three types of relationships of stoichiometric calculations
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Mass–Mass Relationship
ww
w
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2
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3
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Q
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Stoichiometric calculations are based on balanced chemical
equation and equation is balanced on the basis of Law of conservation of
mass e
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a
llon
line
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e
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Title: Basic concepts
Description: Basic concepts of chemistry with long answers, short answers, and M.C.Qs.
Description: Basic concepts of chemistry with long answers, short answers, and M.C.Qs.