This set of Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Material Balances Involving Ideal Gases”.
1. H2 at 27oC with pressure 10 atm and volume 10 liter is passed through a reactor with 6 moles of oxygen, if the limiting reagent reacts completely, how many moles of oxygen is left unreacted?
a) 1
b) 2
c) 4
d) 6
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Explanation: The reaction is 2H2 + O2 -> 2H2O, moles of H2 passed = 10*10/(0.0821*300) = 4, => moles of H2 reacted = 4, => moles of O2 reacted = 4, => moles of O2 left unreacted = 6 – 2 = 4.
2. N2 with pressure 10 atm and H2 with pressure 30 atm, both with volume 10 liter at 27oC are passed into a reactor, how many moles NH3 is produced?
a) 4
b) 8
c) 12
d) 16
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Explanation: The reaction is N2 + 3H2 -> 2NH3, moles of N2 = 10*10/(0.0821*300) = 4, moles of H2 = 30*10/(0.0821*300) = 12, => extent of reaction = (0 – 4)/(-1) = 4, => moles of NH3 = 4*2 = 8.
3. CH4 with pressure 10 atm and volume 5 liter at 27oC is passed into a reactor with 50% excess oxygen, how many moles of oxygen is left in the products?
a) 2
b) 4
c) 6
d) 8
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Explanation: The reaction is CH4 + 2O2 -> CO2 + 2H2O, moles of CH4 = 10*5/(0.0821*300) = 2, => moles of O2 left = 2*2(50/100) = 2.
4. CO with pressure 10 atm at 27oC is passed through a reactor with O2, what is the pressure of CO2 produced if 60% CO reacted?
a) 2 atm
b) 6 atm
c) 10 atm
d) 14 atm
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Explanation: The reaction is 2CO + O2 -> 2CO2, pressure of CO2 = 10*0.6 = 6 atm.
5. Glucose with pressure 10 atm at 27oC is passed through a reactor with O2, what is the temperature of CO2 produced if pressure becomes thrice?
a) 150 K
b) 240 K
c) 300 K
d) 330 K
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Explanation: The reaction is C6H12O6+ 9O2 -> 6CO2 + 6H2O, => 30/T = 6(10/300), => T = 150 K.
6. A gas mixture with 6% O2 with pressure 1 atm at 27oC is entered a reactor with rate F, and another stream with pure O2 with 2 atm pressure at 27oC entered the reactor with rate 1 liter/s, product has 10% O2 with same conditions with rate P, what is the value of F?
a) 575.5 liter/s
b) 725 liter/s
c) 895 liter/s
d) 997.5 liter/s
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Explanation: Overall material balance: F + 1 = P, O2 balance: 0.06*F + 2*1*1 = 0.1*P, => 6F + 400 = 10P, => F = 399*2.5= 997.5 liter/s.
7. A mixture with 60% O2 and 40% H2 with pressure 5 Pa at 27oC at the rate 15 liter/s is passed through a reactor with another stream containing pure H2 with pressure 10 Pa at 27oC at the rate 5 liter/s, what is the fraction of H2 with pressure 5 Pa at 27oC in product?
a) 0.2
b) 0.4
c) 0.6
d) 0.8
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Explanation: Overall material balance: 15 + 5 = P, => P = 20 mole/s, Overall O2 balance: 0.4*5*15 + 1*10*5 = 20*x*5, => x = 0.8.
8. A gas mixture has 10% CH4 with pressure 5 Pa at 27oC at the rate F, is passed through a reactor with another stream containing 60% CH4 with pressure 5 Pa at -73oC at the rate 10 liter/s, if the percentage of CH4 with pressure 5 Pa at 27oC in product is 80%, what is the value of F?
a) 1 liter/s
b) 1.4 liter/s
c) 2 liter/s
d) 2.6 liter/s
View answer
Explanation: Overall material balance: F + 10 = P, Overall CH4 Balance: 0.1*F*5/300 + 0.6*10*5/200 = 0.8*P*5/300, => F + 90 = 8P, => F = 10/7 = 1.4 liter/s.
9. A gas mixture with 50% H2 at the rate F is passed through a reactor and it produced a gas mixture with 80% H2 at the rate 15 liter/s, what is the value of F?
a) 5 liter/s
b) 8 liter/s
c) 15 liter/s
d) 24 liter/s
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Explanation: Overall H2 balance: 0.5F = 0.8*15, => F = 24 liter/s.
10. A gas mixture with 20% O2 with pressure 100 Pa at 27oC at the rate 50 liter/s is passed through a reactor and products a gas mixture with 40% O2 with pressure 25 Pa at 27oC, what is the rate of product?
a) 50 liter/s
b) 100 liter/s
c) 200 liter/s
d) 400 liter/s
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Explanation: O2 balance: 0.2*100*50 = 0.4*25*P, => P = 100 liter/s.
11. A gas mixture with 10% H2 with pressure 15 Pa at 27oC at the rate 20 liter/s is passed through a reactor and products a gas mixture with 30% H2 with pressure 25 Pa at 27oC, what is the rate of product?
a) 4 liter/s
b) 10 liter/s
c) 24 liter/s
d) 30 liter/s
View answer
Explanation: H2 balance: 0.1*15*20 = 0.3*25*P, => P = 4 liter/s.
12. A gas mixture with 50% Ar with pressure 80 Pa at 0oC at the rate 5 liter/s is passed through a reactor and products a gas mixture with 80% Ar with pressure 50 Pa at 27oC, what is the rate of product?
a) 5 liter/s
b) 10 liter/s
c) 20 liter/s
d) 40 liter/s
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Explanation: Ar balance: 0.5*80*5 = 0.8*50*P, => P = 5 liter/s.
13. A gas mixture with 5% Neon with pressure 10 atm at 27oC is entered a reactor with rate F, and another stream with pure Neon with 8 atm pressure at 27oC entered the reactor with rate 3 liter/s, product has 10% Neon with same conditions with rate P, what is the value of F?
a) 3 liter/s
b) 15 liter/s
c) 48 liter/s
d) 72 liter/s
View answer
Explanation: Neon balance- 0.05*F*10 + 3*1*8 = 0.1*P*8, => 0.5F + 24 = 0.8P, Overall balance- F + 3 = P, => 0.3F = 21.6, => F = 72 liter/s.
14. CH4 with pressure 10 atm and volume 10 liter at 27oC is passed into a reactor with 20% excess oxygen, how many moles of oxygen is left in the products?
a) 2
b) 4
c) 6
d) 8
View answer
Explanation: The reaction is CH4 + 2O2 -> CO2 + 2H2O, moles of CH4 = 10*10/(0.0821*300) = 4, => moles of O2 left = 2*4(50/100) = 4.
15. A gas mixture with 20% Neon with pressure 3 atm at 27oC is entered a reactor with rate F, and another stream with pure Neon with 2 atm pressure at 27oC entered the reactor with rate 5 liter/s, product has 40% Neon with same conditions with rate P, what is the value of F?
a) 3 liter/s
b) 15 liter/s
c) 30 liter/s
d) 45 liter/s
View answer
Explanation: Neon balance- 0.2*F*3 + 5*2*1 = 0.4*P*2, => 0.6F + 10 = 0.8P, Overall balance- F + 5 = P, => F = 30 liter/s.
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