This set of Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Species Material Balances”.
1. A reactor is supplied with 6 moles of CO and 3 moles of O2 and produced 4 moles of CO2, what is the extent of reaction?
a) 1
b) 2
c) 3
d) 4
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Explanation: The reaction is 2CO + O2 -> 2CO2, => Extent of reaction = (4 – 0)/2 = 2.
2. A reactor is supplied with 6 moles of N2 and 9 moles of H2, if 3 moles of NH3 is produced, how many moles of H2 are left at the end?
a) 1.5
b) 3
c) 4.5
d) 6
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Explanation: The reaction is N2 + 3H2 -> 2NH3, => extent of reaction = (3 – 0)/2 = 1.5, => moles of H2 left = 9 – 1.5*3 = 4.5.
3. A reactor is supplied with 10 moles of CH4 and 10 moles of O2, if the extent of reaction is 3, what are the moles of CO2 produced?
a) 3
b) 6
c) 8
d) 12
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Explanation: The chemical reaction is CH4 + 2O2 -> CO2 + 2H2O, => moles of CO2 produced = 3*1 = 3.
4. A reactor is supplied with 10 moles of O2 and 10 moles of H2, if the extent of reaction is 5, how many moles of water is produced?
a) 5
b) 10
c) 15
d) 20
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Explanation: The chemical reaction is 2H2 + O2 -> 2H2O, => moles of H2O produced = 5*2 = 10.
5. A reactor is supplied with 5 moles of KNO3 and some H2SO4, if the extent of reaction is 2, how many moles of H2SO4 were supplied?
a) 1
b) 2
c) 5
d) Cannot be determined
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Explanation: Since the final moles of H2SO4 are not given, initial moles cannot be determined.
6. A reactor is supplied with a 100 mole feed of composition 46% C3H7O4, 44% O2 and 10% N2, if 50% of the limiting reagent is converted into product, what is the extent of reaction?
a) 1
b) 2
c) 3
d) 4
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Explanation: The reaction is 4C3H7O4 + 11O2 -> 12CO2 + 14H2O, => limiting reagent is O2, => Extent of reaction = (44*0.5 – 44)/(-11) = 2.
7. A reactor is supplied with a feed of composition 46% C3H7O4, 44% O2 and 10% N2, if 50% of the limiting reagent is converted into product, what is the percentage of O2 in the product?
a) 10
b) 18
c) 38
d) 54
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Explanation: The reaction is 4C3H7O4 + 11O2 -> 12CO2 + 14H2O, => Limiting reagent is O2. Let 100 moles of feed was supplied, => after the reaction, moles of CO2 = 24, moles of H2O = 28, moles of O2 = 22, moles of C3H7O4 = 38, moles of N2 = 10, => percentage of O2 = 18%.
8. A reactor is supplied with a feed of composition 46% C3H7O4, 44% O2 and 10% N2, if 50% of the limiting reagent is converted into product, what is the percentage of N2 in the product?
a) 8
b) 18
c) 34
d) 46
View answer
Explanation: The reaction is 4C3H7O4 + 11O2 -> 12CO2 + 14H2O, => Limiting reagent is O2. Let 100 moles of feed was supplied, => after the reaction, moles of CO2 = 24, moles of H2O = 28, moles of O2 = 22, moles of C3H7O4 = 38, moles of N2 = 10, => percentage of N2 = 8%.
9. A reactor is supplied with a feed of composition 46% C3H7O4, 44% O2 and 10% N2, if 50% of the limiting reagent is converted into product, what is the percentage of C3H7O4 in the product?
a) 10
b) 16
c) 31
d) 43
View answer
Explanation: The reaction is 4C3H7O4 + 11O2 -> 12CO2 + 14H2O, => Limiting reagent is O2. Let 100 moles of feed was supplied, => after the reaction, moles of CO2 = 24, moles of H2O = 28, moles of O2 = 22, moles of C3H7O4 = 38, moles of N2 = 10, => percentage of C3H7O4 = 31%.
10. A reactor is supplied with a feed of composition 46% C3H7O4, 44% O2 and 10% N2, if 50% of the limiting reagent is converted into product, what is the percentage of H2O in the product?
a) 15
b) 23
c) 39
d) 51
View answer
Explanation: The reaction is 4C3H7O4 + 11O2 -> 12CO2 + 14H2O, => Limiting reagent is O2. Let 100 moles of feed was supplied, => after the reaction, moles of CO2 = 24, moles of H2O = 28, moles of O2 = 22, moles of C3H7O4 = 38, moles of N2 = 10, => percentage of H2O = 23%.
11. A reactor is supplied with two steams with equal flow rates, stream-1 containing 75% SO2, 25% N2 and stream-2 containing pure H2S, if the product has 1200 grams of S, and the ratio of H2S to H2O is 5 and the ratio of SO2 to H2S is 2, what is the rate of streams?
a) 10 mole
b) 20 moles
c) 30 moles
d) 40 moles
View answer
Explanation: The reaction is 2H2S + SO2 -> 3S + H2O, => extent of reaction, E = (1200/32)/3 = 12.5, Let the rate be F. nSO2p = 2nH2Sp, => 0.75F – E = 2(F – 2E), => 1.25F = 3(12.5), => F = 30 moles.
12. A reactor is supplied with two steams with equal flow rates, stream-1 containing 75% SO2, 25% N2 and stream-2 containing pure H2S, if the product has 1200 grams of S, and the ratio of H2S to H2O is 5 and the ratio of SO2 to H2S is 2, what fraction of limiting reagent is converted into product?
a) 0.21
b) 0.46
c) 0.73
d) 0.83
View answer
Explanation: The reaction is 2H2S + SO2 -> 3S + H2O, => extent of reaction, E = (1200/32)/3 = 12.5, Let the rate be F. nSO2p = 2nH2Sp, => 0.75F – E = 2(F – 2E), => 1.25F = 3(12.5), => F = 30 moles, => limiting reagent is H2S, => fraction of H2S converted into product = 2E/F = 2(1.25)/3 = 0.83.
13. A reactor is supplied with two steams with equal flow rates, stream-1 containing 75% SO2, 25% N2 and stream-2 containing pure H2S, if the product has 1200 grams of S, and the ratio of H2S to H2O is 5 and the ratio of SO2 to H2S is 2, how many moles of water are produced?
a) 1
b) 2
c) 3
d) 4
View answer
Explanation: The reaction is 2H2S + SO2 -> 3S + H2O, => extent of reaction, E = (1200/32)/3 = 12.5, Let the rate be F. nSO2p = 2nH2Sp, => 0.75F – E = 2(F – 2E), => 1.25F = 3(12.5), => F = 30 moles. 5nH2Op = nH2Sp, => 5 nH2Op = 30 – 2(12.5) = 5, => nH2Op = 1.
14. A reactor is supplied with two steams with equal flow rates, stream-1 containing 75% SO2, 25% N2 and stream-2 containing pure H2S, if the product has 1200 grams of S, and the ratio of H2S to H2O is 5 and the ratio of SO2 to H2S is 2, what fraction of excess reagent is converted into product?
a) 0.23
b) 0.55
c) 0.74
d) 0.87
View answer
Explanation: The reaction is 2H2S + SO2 -> 3S + H2O, => extent of reaction, E = (1200/32)/3 = 12.5, Let the rate be F. nSO2p = 2nH2Sp, => 0.75F – E = 2(F – 2E), => 1.25F = 3(12.5), => F = 30 moles. => The excess reagent is SO2, => fraction of SO2 converted into product = E/0.75F = 12.5/(0.75*30) = 0.55.
15. A reactor is supplied with two steams with equal flow rates, stream-1 containing 75% SO2, 25% N2 and stream-2 containing pure H2S, if the product has 1200 grams of S, and the ratio of H2S to H2O is 5 and the ratio of SO2 to H2S is 2, what is percentage of Sulfur in the product?
a) 23%
b) 47%
c) 61%
d) 84%
View answer
Explanation: The reaction is 2H2S + SO2 -> 3S + H2O, => extent of reaction, E = (1200/32)/3 = 12.5, Let the rate be F. nSO2p = 2nH2Sp, => 0.75F – E = 2(F – 2E), => 1.25F = 3(12.5), => F = 30 moles. => Moles of SO2 = 0.75F – E = 10, moles of H2S = F – 2E = 5, moles of N2 = 7.5, moles of S = 37.5, moles of H2O = 1, => percentage of sulfur = 61%.
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