Question

 1. How much mass of silver nitrate will react with 5.85 g of sodium chloride to produce 14.35 g of silver chloride and 8.5 g of sodium nitrate if law of conservation of mass is followed? *

(a) 22.85 g

(b) 108 g

(c) 17.0 g

(d) 28.70 g

Q 2. Choose the molecular formula of an oxide of iron in which the mass per cent of iron and oxygen are 69.9 and 30.1 respectively and its molecular mass is 160. *

(a) FeO

(b) Fe₃O₄

(c) Fe₂0₃

(d) FeO₂

Q 3. How many electrons are there in the valence shell of the O²⁻ ion? *

(a) 2

(b) 4

(c) 10

(d) 8

Q 4 Two atoms are said to be isobars if. *

(a) they have same atomic number but different mass number.

(b) they have same number of electrons but different number of neutrons

(c) they have same number of neutrons but different number of electrons.

(d) sum of the number of protons and neutrons is same but the number of protons is different.

Q 5. Which of the following is responsible to rule out the existence of definite paths or trajectories of electrons? *

(a) Pauli’s exclusion principle.

(b) Hund’s rule of maximum multiplicity.

(c) Aufbau principle.

(d) Heisenberg’s uncertainty principle.
​

Answer 1

ANSWER

1) According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants

For the chemical reaction: AgNO

3

+NaCI→NaNO

3

+AgCI

m

reactants

=m

products

m

AgNO

3

+m

NaCl

=m

NaNO

3

+m

AgCl

x+5.85=8.5+14.35

x=17.0 g

option C is correct

2) Let the molecule be Fe

a

O

b

∴ mass % of iron × molar mass of Fe

x

O

y

= Atomic mass of iron × a

100

69.9

×160=56a

a=2

Similarly for oxygen

100

30.1

×160=16b

b=3

Molecular formula is Fe2O3

3) O has 6 electrons in it's valence shell. Adding two electrons make the valence shell electrons to 8.

4)A. Elements with same atomic number but different mass number are called isotopes.

B. Elements with same number of electrons but different number of neutrons are called isotopes.

C. Elements with same number of neutrons but different number of electrons are called isotones.

D. If the Sum of the number of protons and neutrons (is equal to mass number of an atom) is same but the number of protons is different the atoms are called isobars.

5) Affbau principle