Chemistry Test Gas Laws 4 — Questions and Answers
Question 1: Using PV = nRT, what is the pressure of 0.5 mol of gas in a 10.0 L container at 300 K? (R = 0.0821 L·atm/mol·K)
- 0.62 atm
- 1.23 atm (Correct answer)
- 2.46 atm
- 0.31 atm
Correct answer: 1.23 atm
P = nRT/V = (0.5)(0.0821)(300)/10.0 = 1.23 atm.
Question 2: Graham's Law of Effusion states that the rate of effusion is inversely proportional to which property?
- Temperature
- Pressure
- Square root of molar mass (Correct answer)
- Volume
Correct answer: Square root of molar mass
Graham's Law: rate ∝ 1/√M, so heavier gases effuse more slowly.
Question 3: Which gas effuses faster: H2 (M = 2 g/mol) or O2 (M = 32 g/mol), and by what factor?
- O2, by a factor of 4
- H2, by a factor of 4 (Correct answer)
- H2, by a factor of 16
- O2, by a factor of 16
Correct answer: H2, by a factor of 4
Rate ratio = √(32/2) = √16 = 4, so H2 effuses 4 times faster than O2.
Question 4: A real gas deviates most from ideal behavior under which conditions?
- High temperature and low pressure
- Low temperature and high pressure (Correct answer)
- High temperature and high pressure
- Low temperature and low pressure
Correct answer: Low temperature and high pressure
At low temperature and high pressure, intermolecular forces and molecular volume become significant, causing deviation from ideal behavior.
Question 5: What is the mole fraction of N2 in a mixture where N2 has a partial pressure of 0.8 atm and total pressure is 2.0 atm?
- 0.2
- 0.4 (Correct answer)
- 0.6
- 0.8
Correct answer: 0.4
Mole fraction = partial pressure / total pressure = 0.8/2.0 = 0.4.
Question 6: A gas sample at 25°C and 1.0 atm occupies 3.0 L. What volume does it occupy at 50°C and 1.0 atm?
- 6.0 L
- 3.25 L (Correct answer)
- 2.75 L
- 1.5 L
Correct answer: 3.25 L
Charles's Law: V2 = V1T2/T1 = 3.0 × (323/298) = 3.25 L (temperatures in Kelvin).
Question 7: Which of the following is assumed about molecular collisions in the kinetic molecular theory?
- Collisions are inelastic and lose energy
- Collisions are perfectly elastic with no net energy loss (Correct answer)
- Molecules stick together after colliding
- Only collisions with the container walls matter
Correct answer: Collisions are perfectly elastic with no net energy loss
KMT assumes all molecular collisions are perfectly elastic, conserving total kinetic energy.
Chemistry Test Gas Laws 4
Using PV = nRT, what is the pressure of 0.5 mol of gas in a 10.0 L container at 300 K? (R = 0.0821 L·atm/mol·K)