Chemical Engineering Questions and Answers – Species Material Balances

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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
View answer

Answer: b
Explanation: The reaction is 2CO + O2 -> 2CO2, => Extent of reaction = (4 – 0)/2 = 2.
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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
View answer

Answer: c
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
View answer

Answer: a
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
View answer

Answer: b
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
View answer

Answer: d
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
View answer

Answer: b
Explanation: The reaction is 4C3H7O4 + 11O2 -> 12CO2 + 14H2O, => limiting reagent is O2, => Extent of reaction = (44*0.5 – 44)/(-11) = 2.
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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
View answer

Answer: b
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

Answer: a
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

Answer: c
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

Answer: b
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

Answer: c
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

Answer: d
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.
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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

Answer: a
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

Answer: b
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

Answer: c
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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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn