CART - Chemistry Acceleration Readiness Gas Laws and Properties Questions and Answers — Questions and Answers
Question 1: A flexible container holds 25.0 L of a gas at a pressure of 3.50 atm. If the temperature and number of moles of the gas remain constant, what is the new volume if the pressure is increased to 5.00 atm?
- 12.5 L
- 17.5 L (Correct answer)
- 35.7 L
- 87.5 L
Correct answer: 17.5 L
This question applies Boyle's Law, which states that for a fixed amount of gas at constant temperature, the pressure and volume are inversely proportional (P₁V₁ = P₂V₂). [3, 5] To find the new volume (V₂), we can rearrange the formula to V₂ = (P₁V₁) / P₂. Plugging in the values: V₂ = (3.50 atm * 25.0 L) / 5.00 atm = 17.5 L.
Question 2: A balloon contains 5.0 L of air at 27°C. If the pressure remains constant, to what temperature in Celsius must the balloon be heated to expand its volume to 8.0 L?
- 43.2°C
- 207°C (Correct answer)
- 480°C
- 753°C
Correct answer: 207°C
This problem requires the use of Charles's Law, which describes the direct relationship between the volume and absolute temperature of a gas at constant pressure (V₁/T₁ = V₂/T₂). [7, 8] First, convert the initial temperature to Kelvin: T₁ = 27°C + 273.15 = 300.15 K. Then, rearrange the formula to solve for the final temperature (T₂): T₂ = (V₂ * T₁) / V₁. Plugging in the values: T₂ = (8.0 L * 300.15 K) / 5.0 L = 480.24 K. Finally, convert the temperature back to Celsius: T₂ = 480.24 K - 273.15 = 207.09°C.
Question 3: Which of the following statements is NOT a postulate of the Kinetic Molecular Theory of ideal gases?
- Gas particles are in constant, random, straight-line motion.
- The volume of the gas particles themselves is significant compared to the total volume of the container. (Correct answer)
- Collisions between gas particles are perfectly elastic, meaning no kinetic energy is lost.
- The average kinetic energy of gas particles is directly proportional to the absolute temperature (in Kelvin).
Correct answer: The volume of the gas particles themselves is significant compared to the total volume of the container.
The Kinetic Molecular Theory of ideal gases includes several key postulates. One of these is that the volume of the individual gas particles is considered negligible compared to the vast empty space between them. [4, 12] Therefore, the statement that the particle volume is significant contradicts this fundamental assumption of an ideal gas.
Question 4: A rigid 10.0 L container holds a mixture of nitrogen gas (N₂) and oxygen gas (O₂). The partial pressure of the nitrogen is 0.75 atm and the partial pressure of the oxygen is 0.25 atm. What is the total pressure inside the container?
- 0.50 atm
- 0.75 atm
- 1.00 atm (Correct answer)
- Cannot be determined from the information given.
Correct answer: 1.00 atm
This scenario is an application of Dalton's Law of Partial Pressures. This law states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases (P_total = P₁ + P₂ + ...). [10, 11, 21] In this case, P_total = P_N₂ + P_O₂ = 0.75 atm + 0.25 atm = 1.00 atm.
Question 5: A sample of 0.50 moles of an ideal gas is held in a 10.0 L container at a temperature of 298 K. What is the pressure of the gas? (R = 0.0821 L·atm/mol·K)
- 0.82 atm
- 1.22 atm (Correct answer)
- 2.45 atm
- 12.2 atm
Correct answer: 1.22 atm
This problem requires the use of the Ideal Gas Law, PV = nRT. [9, 23] To find the pressure (P), we can rearrange the equation to P = nRT / V. Plugging in the given values: P = (0.50 mol * 0.0821 L·atm/mol·K * 298 K) / 10.0 L. This calculation results in a pressure of 1.22 atm.
Question 6: Under which of the following conditions would a real gas be expected to deviate MOST from ideal gas behavior?
- High temperature and high pressure
- Low temperature and high pressure (Correct answer)
- High temperature and low pressure
- Low temperature and low pressure
Correct answer: Low temperature and high pressure
Real gases deviate from ideal behavior because the assumptions of the Kinetic Molecular Theory (negligible particle volume and no intermolecular forces) break down. [23] At low temperatures, gas particles move slower and intermolecular forces become more significant. At high pressures, the particles are forced closer together, making their individual volumes a more significant fraction of the total container volume. Therefore, the combination of low temperature and high pressure causes the most significant deviation from ideal behavior.
CART - Chemistry Acceleration Readiness Gas Laws and Properties Questions and Answers
A flexible container holds 25.0 L of a gas at a pressure of 3.50 atm.
If the temperature and number of moles of the gas remain constant, what is the new volume if the pressure is increased to 5.00 atm?