Mole Concept

Question 1

Define moles if weight of the compound is given.

Answer 1

Moles = Weight/Molecular Mass

Question 2

Define moles if entities of the compound is given.

Answer 2

Moles = Entities(atoms, molecules, ions)/Avagadro’s Number(NA)

Question 3

Define moles if volume at stp given.

Answer 3

Moles = Volumes(litres)/22.4

Question 4

Percentage composition of element is

Answer 4

(Atomic Weight of element*No. of atoms *100)/ Molecular Weight of Compounds

Question 5

Calculate the percentage composition of all the elements in CaCO3

Answer 5

Ca- 40%, C- 12%, O- 48%

Question 6

Absolute density of solids and liquid

Answer 6

Mass/Volume

Question 7

Relative density of solids and liquid

Answer 7

Density of substance/ Density of H2O at 4°C

Question 8

Absolute density of gases

Answer 8

From the ideal gas equation, density = PM/RT

Question 9

Relative density of gases

Answer 9

The density of a gas w.r.t another gas at constant temperature and pressure

Question 10

Vapour density of gases

Answer 10

The density of a gas w.r.t H2 gas at constant temperature and pressure

Question 11

Calculate the relative density of CH4 w.r.t O2

Answer 11

1/2

Question 12

Average Atomic Weight formula

Answer 12

(% abundance* At. wt.1 + % abundance*At. wt2)/100

Question 13

Mean Molar Mass Formula

Answer 13

(n1M1 + n2M2)/ n1 + n2

Question 14

For reaction 2A+ B→ A2B. 5 moles of A are reacted with 10 moles of B. Hence the limiting reagent and the moles of A2B formed are:

Answer 14

A, 2.5

Question 15

C3H8 + 5O2 → 3CO2 + 4H2O
If 2.5 moles of C3H8 are present, then how many moles of CO2 are formed using the stoichiometry method?

Answer 15

7.5 moles of CO2 are formed

Question 16

What is the relation between empirical and molecular formulas?

Answer 16

M.F. = (E.F.)n, where n = MFW/EFW

Question 17

Define molarity(M).

Answer 17

Molarity is the ratio of moles of solute and volume of solution in litre.

Question 18

Define molality(m)

Answer 18

Molality is the ratio of moles of solute and weight of solvent in kg.

Question 19

Define mole fraction

Answer 19

(Number of moles of A)/ (Number of moles of A+ number of moles of B)