# Chemical Process Calculation Questions and Answers – Mole and Molecular Weight-III

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This set of Chemical Process Calculation Multiple Choice Questions & Answers (MCQs) focuses on “Mole and Molecular Weight-III”.

1. How many gm moles oxygen are there in 88 gms carbon di oxide?
a) 1
b) 2
c) 3
d) 4

Explanation: 88gms of CO2 = 2 moles of CO2 = 4 moles of oxygen.

2. What is the percent water in CuSO4.5H2O?
a) 12
b) 14
c) 16
d) 18

Explanation: Percentage water = mass of water in the molecule/Total mass of the molecule.

3. What is the average molecular weight of a gas containing 20% N2 (molecular wt. = 28) and 80% SO2 (molecular wt. = 64)?
a) 28.4
b) 56.8
c) 24.4
d) 48.8

Explanation: Take 1 gm mole of the Gas and then average molecular weight = 0.20×28+0.80×64.
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4. Two statements are given as
(1) When a percentage of fractions is given for gas, it is assumed that it refers to a mole fraction
(2) When a percentage of fractions is given for liquid or solid, it is assumed that it refers to the weight fraction
True statements are
a) 1
b) 2
c) Both 1 and 2
d) Neither 1 nor 2

Explanation: This is a simple assumption, unless otherwise specified.

5. A bucket contains 10 kg of water and 10 kg of NaOH. The respective mass fraction of water and the mole fraction of NaOH are
a) 0.5 and 0.31
b) 1.0 and 0.62
c) 0.5 and 0.69
d) 1.0 and 0.50

Explanation: Mole fraction of X = moles of X/total moles and mass fraction of X = mass of X/total mass.

6. What is the formula for a solid compound that contains 42.11% C, 51.46% O, and 6.43% H and having molecular weight about 341.
a) C10 O12H29
b) C11O13 H
c) C12O11H22
d) C12O10H37

Explanation: Take 100 g of the compound and calculate the ratio of the molecules, then make it integer to get the chemical formula.

7. If in a compound the moles of consisting atoms are doubled then the mole fraction of a particular atom will be
a) Double
b) Half
c) Remain same
d) None of the mentioned

Explanation: mole fraction of X = moles of the X/total moles.

8. Select the correct statement
a) 1 mole of SO2 and 64 g of Ethyl Chloride have same number of moles
b) 1 mole of SO2 and 64 g of Ethyl Chloride don`t have same molecular weights
c) Both a and b
d) Neither a nor b

Explanation: 1 mole of SO2 = 64 g = 1 mole of Ethyl Chloride.

9. What is a mole?
a) A mole is found in a certain number of cm3 of one substance or another.
b) A mole is the sum of atomic weights.
c) A mole is the number of molecules in one gram of a substance.
d) None of the mentioned

Explanation: A mole is number of molecules.

10. What will be the molecular weight of a chemical, consisting 2 moles of H2SO4, 3 moles of SO2 and 1 mole of NaOH?
a) 128
b) 228
c) 328
d) 428

Explanation: Molecular weight = 2 moles of H2SO4(98)+3 moles of SO2(64)+1 mole of NaOH(40).

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