250+ TOP MCQs on Material Balance Concept and Answers

Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) on “Material Balance Concept”.

1. Which of the following does the concept of material balance based upon?
a) Conservation of mass
b) Conservation of energy
c) Conservation of momentum
d) Conservation of Volume
Answer: a
Clarification: Material is simply conservation of mass.

2. The equation of material balance, (Final condition + Sum of outputs) is equal to which of the following?
a) Initial condition – Sum of inputs
b) Initial condition + Sum of inputs
c) Sum of inputs – Initial condition
d) None of the mentioned
Answer: b
Clarification: Equation of material balance is Final condition – Initial condition = Sum of inputs – Sum of outputs, => Final condition + Sum of outputs = Initial condition + Sum of inputs.

3. A container has 10 grams of water 5 grams of water is added and 2 grams of water is taken out, what is the final amount of water?
a) 7 grams
b) 10 grams
c) 13 grams
d) 15 grams
Answer: c
Clarification: Final condition = Initial condition + sum of inputs – sum of outputs = 10 + 5 – 2 = 13 grams.

4. 10 moles of O₂ is added to 10 moles of H₂, how many moles of H₂O will it produce?
a) 5
b) 10
c) 15
d) 20
Answer: b
Clarification: Balanced equation is 2H₂ + O₂ -> 2H₂O, => Moles of H₂O = Moles of H₂ = 10.

5. A combustion reaction has reactants 1 mole of C_xH_y and 2 moles of O₂ and products 1 mole of CO₂ and 2 mole of H₂O, what is x + y?
a) 1
b) 3
c) 4
d) 5
Answer: d
Clarification: Moles of C, H and O in reactants = Moles of C, H and O in products, => C: 1*x = 1*1 => x = 1, H: 1*y = 2*2 => x + y = 5.

6. In a random reaction 2 mole of CH₄ and 1 mole of C₂H₄ are reacted, and 1 mole of C₃H₈ and 1 mole of C_xH_y are produced, what is x*y?
a) 2
b) 4
c) 8
d) 12
Answer: b
Clarification: Material balance for C: 2*1 + 1*2 =1*3 +1*x, => x = 1, for H: 2*4 + 1*4 = 1*8 + 1*y, => y = 4, => x*y = 4.

7. A reaction has reactants 2 moles of NaOH and 1 mole of H₂SO₄, and products Na₂SO₄ and H₂O, what are the total moles of products?
a) 1
b) 2
c) 3
d) 4
Answer: c
Clarification: Material Balance for Na: 2*1 = n1*2 => n1 = 1, for H: 2*1 + 1*2 = n2*2 => n2 = 2, => total moles of products = 1 + 2 = 3.

8. A reaction is A + 2B -> 3C, if 2 moles of A and 4 moles of B entered the system, what are the number of moles of C formed?
a) 2
b) 4
c) 6
d) 8
Answer: c
Clarification: Moles of C = 3*2 = 6.

9. 10 moles of A were present in a system initially, and 10 moles are added to it, it follows the reaction 4A -> B, what are the number of moles of B produced?
a) 5
b) 10
c) 15
d) 20
Answer: a
Clarification: Moles of B = (10 + 10)/4 = 5.

10. 10 moles of A were present in a system initially, and 10 moles of C are added to it, it follows the reaction 2A + C -> 5B, what is the number of moles of B produced?
a) 5
b) 10
c) 25
d) 50
Answer: c
Clarification: Mole of B = 5*5 = 25.

11. There were 10 moles of a substance present initially in a system, 5 moles were added to it and a reaction occurred so that its moles are reduced by 20%, what are the final moles of a substance in the system?
a) 10
b) 12
c) 15
d) 18
Answer: b
Clarification: Final moles of substance = (10 + 5)*80/100 = 12.

12. There were 15 moles of a substance present initially in a system, 25 moles were added to it and a reaction occurred so that its moles are reduced by 50%, what are the final moles of a substance in the system?
a) 10
b) 15
c) 20
d) 40
Answer: c
Clarification: Final moles of substance = (15 + 25)*50/100 = 20.

13. 10 moles of A were present in a system initially, and 12 moles of C are added to it, it undergoes the reaction 2A + 3C -> 2B, what are number of moles of B produced?
a) 4
b) 5
c) 8
d) 12
Answer: c
Clarification: Moles of B = 2*4 = 8.

14. 10 moles of A were present in a system initially, and 8 moles of C are added to it, it undergoes the reaction 5A + 3C -> 4B, what are number of moles of B produced?
a) 4
b) 6
c) 8
d) 10
Answer: c
Clarification: Moles of B = 4*2 = 8.

15. 8 moles of A were present in a system initially, and 24 moles of B are added to it, it undergoes the reaction 2A + 3B -> 4C + 5D, what are the number of moles of D produced?
a) 10
b) 20
c) 30
d) 40
Answer: c
Clarification: Moles of D = 5*4 = 20.