# Chemical Engineering Questions and Answers – Ideal Gas Mixtures and Partial Pressure

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This set of Chemical Engineering Test focuses on “Ideal Gas Mixtures and Partial Pressure”.

1. A container has two gases at 27oC, one with molar volume 6 L/mole, another with molar volume 3 L/mole, what is the total pressure of the container?
a) 6.9 atm
b) 8.5 atm
c) 12.3 atm
d) 15.8 atm

Explanation: p1V1 = n1RT1, => p1 = 0.0821*300/6 = 4.1 atm, p2 = 0.0821*300/3 = 8.2 atm, => P = 4.1 + 8.2 = 12.3 atm.

2. The fraction of gas in a container is 0.1, if the total pressure of the container is 10 atm, what is the partial pressure of the gas?
a) 1 atm
b) 5 atm
c) 10 atm
d) 20 atm

Explanation: Partial pressure of gas = 0.1*10 = 1 atm.

3. The fraction of gas in a container is 0.5, if the total volume of the container is 6 liter, what is the volume of the gas?
a) 2 liter
b) 3 liter
c) 5 liter
d) 6 liter

Explanation: Volume of gas = Volume of container = 6 liter.
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4. A gas mixture contains 30% CO2, 40% O2, 30% N2, if the partial pressure of CO2 is 6 Pa, what is the total pressure of gas mixture?
a) 6 Pa
b) 10 Pa
c) 20 Pa
d) 60 Pa

Explanation: 0.3*P = 6, => P = 20 Pa.

5. The highest pressure gas of a mixture has partial pressure p, the partial pressure of other gases decreases by factor of 2n-1, the partial pressure of second gases decreases by a factor of 2, partial pressure of third gas increases by 4, and so on, if the total pressure of gas mixture is 31p/16, how many gases are present in the mixture?
a) 3
b) 5
c) 10
d) 15

Explanation: Let n gases are present in the mixture, => p + p/2 + p/4 + – – – + p/2n-1 = 7p/8, => p(1 – 1/2n)/(1 – ½) = 31p/16, => n = 5.

6. A gas mixture comprises of 20% CO2, 50% O2, and 30% N2 has the total pressure 100 Pa at temperature -73oC, if the temperature is increased to 27oC, what is the new partial pressure of N2?
a) 15 Pa
b) 30 Pa
c) 45 Pa
d) 60 Pa

Explanation: P1/P2 = T1/T2, => 100/P2 = 200/300, => P2 = 150 Pa, => new partial pressure of N2 = 0.3*150 = 45 Pa.

7. A container has gas mixture of 20% H2 and 80% N2 with total pressure P, now same amount of O2 is added to the mixture, what is the new partial pressure of N2?
a) 0.2P
b) 0.8P
c) P
d) 1.6P

Explanation: New partial pressure of N2 = Old partial pressure of N2 = 0.8P.

8. A container has gas mixture of 40% CO2 and 60% H2 with total pressure 10 Pa, if now O2 is added to it isothermally so that the final composition of the mixture becomes 20% CO2, 30% H2, and 50% O2, what is the partial pressure of O2 in the new composition?
a) 5 Pa
b) 10 Pa
c) 20 Pa
d) 35 Pa

Explanation: Partial pressure of H2 = 0.6*10 = 6 Pa, => Partial pressure of O2 = 0.5*6/0.3 = 10 Pa.

9. A gas mixture has 30% O2, 40% H2, and 30% N2 with molar volume of N2 10 L/mole at temperature 27oC, what is the partial pressure of H2?
a) 2.4 atm
b) 3.6 atm
c) 4.8 atm
d) 6.4 atm

Explanation: Molar volume of H2 = molar volume of N2 = 10 L/mole, PV = nRT, => P*10 = 0.0821*300, => P = 2.4 atm.

10. A gas mixture contains 20% CO, 30% SO2, and 50% N2, if the partial pressure of N2 is 5 atm at 27oC, what is the molar volume of N2?
a) 2.4 liter
b) 3.7 liter
c) 4.9 liter
d) 5.6 liter

Explanation: Total pressure of mixture = 5/0.5 = 10 atm, => Molar Volume of N2 = Total molar volume of mixture = 0.0821*300/10 = 2.4 liter.

11. What is the total pressure of contained if it contains 0.5 fraction of O2 with partial pressure 3 Pa, 0.3 fraction of H2 with partial pressure 5 Pa, 0.2 fraction of CO2 with partial pressure 15 Pa?
a) 6 Pa
b) 7 Pa
c) 8 Pa
d) 9 Pa

Explanation: Total pressure = 0.5*3 + 0.3*5 + 0.2*15 = 6 Pa.

12. What is the total pressure of contained if it contains 0.3 fraction of N2 with partial pressure 8 Pa, 0.3 fraction of H2 with partial pressure 2 Pa, 0.4 fraction of CO2 with partial pressure 15 Pa?
a) 6.4 Pa
b) 7 Pa
c) 8.5 Pa
d) 9 Pa

Explanation: Total pressure = 0.3*8 + 0.3*2 + 0.4*15 = 9 Pa.

13. What is the partial pressure of O2 with fraction 0.1, if the total pressure is 10 Pa?
a) 1 Pa
b) 3 Pa
c) 5 Pa
d) 7 Pa

Explanation: Partial pressure = 0.1*10 = 1 Pa.

14. A container with total volume 10 liter is filled with 20% of O2, 40% of N2, and 40% of CO, what is the volume of O2?
a) 2 liter
b) 4 liter
c) 8 liter
d) 10 liter

Explanation: Volume of each gas in the container is equal to the total volume of the container.

15. A vessel contains 10 moles of O2 and some other gases, total pressure is 10 atm, what is the partial pressure of O2?
a) 1 atm
b) 10 atm
c) 100 atm
d) Cannot be determined

Explanation: Since the total moles are not given, fraction of O2 cannot be determined, so partial pressure of O2 cannot be determined.

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