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

1. A container has two gases at 27^{o}C, 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

View answer

Explanation: p

_{1}V

_{1}= n

_{1}RT

_{1}, => p

_{1}= 0.0821*300/6 = 4.1 atm, p

_{2}= 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

View answer

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

View answer

Explanation: Volume of gas = Volume of container = 6 liter.

4. A gas mixture contains 30% CO_{2}, 40% O_{2}, 30% N_{2}, if the partial pressure of CO_{2} is 6 Pa, what is the total pressure of gas mixture?

a) 6 Pa

b) 10 Pa

c) 20 Pa

d) 60 Pa

View answer

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 2^{n-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

View answer

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% CO_{2}, 50% O_{2}, and 30% N_{2} has the total pressure 100 Pa at temperature -73^{o}C, if the temperature is increased to 27^{o}C, what is the new partial pressure of N_{2}?

a) 15 Pa

b) 30 Pa

c) 45 Pa

d) 60 Pa

View answer

Explanation: P

_{1}/P

_{2}= T

_{1}/T

_{2}, => 100/P

_{2}= 200/300, => P

_{2}= 150 Pa, => new partial pressure of N

_{2}= 0.3*150 = 45 Pa.

7. A container has gas mixture of 20% H_{2} and 80% N_{2} with total pressure P, now same amount of O_{2} is added to the mixture, what is the new partial pressure of N_{2}?

a) 0.2P

b) 0.8P

c) P

d) 1.6P

View answer

Explanation: New partial pressure of N

_{2}= Old partial pressure of N

_{2}= 0.8P.

8. A container has gas mixture of 40% CO_{2} and 60% H_{2} with total pressure 10 Pa, if now O_{2} is added to it isothermally so that the final composition of the mixture becomes 20% CO_{2}, 30% H_{2}, and 50% O_{2}, what is the partial pressure of O_{2} in the new composition?

a) 5 Pa

b) 10 Pa

c) 20 Pa

d) 35 Pa

View answer

Explanation: Partial pressure of H2 = 0.6*10 = 6 Pa, => Partial pressure of O

_{2}= 0.5*6/0.3 = 10 Pa.

9. A gas mixture has 30% O_{2}, 40% H_{2}, and 30% N_{2} with molar volume of N_{2} 10 L/mole at temperature 27^{o}C, what is the partial pressure of H_{2}?

a) 2.4 atm

b) 3.6 atm

c) 4.8 atm

d) 6.4 atm

View answer

Explanation: Molar volume of H

_{2}= molar volume of N

_{2}= 10 L/mole, PV = nRT, => P*10 = 0.0821*300, => P = 2.4 atm.

10. A gas mixture contains 20% CO, 30% SO_{2}, and 50% N_{2}, if the partial pressure of N_{2} is 5 atm at 27^{o}C, what is the molar volume of N_{2}?

a) 2.4 liter

b) 3.7 liter

c) 4.9 liter

d) 5.6 liter

View answer

Explanation: Total pressure of mixture = 5/0.5 = 10 atm, => Molar Volume of N

_{2}= 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 O_{2} with partial pressure 3 Pa, 0.3 fraction of H_{2} with partial pressure 5 Pa, 0.2 fraction of CO_{2} with partial pressure 15 Pa?

a) 6 Pa

b) 7 Pa

c) 8 Pa

d) 9 Pa

View answer

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 N_{2} with partial pressure 8 Pa, 0.3 fraction of H_{2} with partial pressure 2 Pa, 0.4 fraction of CO_{2} with partial pressure 15 Pa?

a) 6.4 Pa

b) 7 Pa

c) 8.5 Pa

d) 9 Pa

View answer

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

13. What is the partial pressure of O_{2} with fraction 0.1, if the total pressure is 10 Pa?

a) 1 Pa

b) 3 Pa

c) 5 Pa

d) 7 Pa

View answer

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

14. A container with total volume 10 liter is filled with 20% of O_{2}, 40% of N_{2}, and 40% of CO, what is the volume of O_{2}?

a) 2 liter

b) 4 liter

c) 8 liter

d) 10 liter

View answer

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

15. A vessel contains 10 moles of O_{2} and some other gases, total pressure is 10 atm, what is the partial pressure of O_{2}?

a) 1 atm

b) 10 atm

c) 100 atm

d) Cannot be determined

View answer

Explanation: Since the total moles are not given, fraction of O

_{2}cannot be determined, so partial pressure of O

_{2}cannot be determined.

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