Questions on Combined Gas Law
Combined Gas Law – Multiple Choice Questions
1. The Combined Gas Law relates which three gas properties?
A) Pressure, volume, and mass
B) Temperature, volume, and density
C) Pressure, temperature, and volume
D) Volume, density, and mass
E) Pressure, volume, and molarity
2. What is the correct formula for the Combined Gas Law?
A) PV = nRT
B) P/T = constant
C) V/T = constant
D) (P × V)/T = constant
E) P × T = V
3. The Combined Gas Law is derived by combining:
A) Avogadro’s and Dalton’s Laws
B) Charles’s and Gay-Lussac’s Laws
C) Boyle’s, Charles’s, and Gay-Lussac’s Laws
D) Newton’s Laws
E) Boyle’s and Avogadro’s Laws
4. Which of the following must be constant in the Combined Gas Law?
A) Temperature
B) Pressure
C) Volume
D) Amount of gas (moles)
E) Mass and volume
5. The formula (P1×V1)/T1=(P2×V2)/T2(P_1 × V_1)/T_1 = (P_2 × V_2)/T_2(P1×V1)/T1=(P2×V2)/T2 assumes that:
A) The gas changes its identity
B) The number of moles is constant
C) The gas turns into a liquid
D) Pressure is always atmospheric
E) Volume and temperature are inversely related
6. If pressure increases while temperature and moles remain constant, what happens to the volume?
A) Increases
B) Decreases
C) Stays the same
D) Doubles
E) Becomes infinite
7. What temperature scale must be used in the Combined Gas Law?
A) Celsius
B) Fahrenheit
C) Kelvin
D) Rankine
E) Centigrade
8. A gas has an initial pressure of 2 atm, volume of 4 L, and temperature of 300 K. If pressure becomes 4 atm and temperature increases to 600 K, what is the final volume?
A) 4 L
B) 6 L
C) 2 L
D) 8 L
E) 1 L
9. If volume and temperature both increase, what generally happens to pressure (assuming constant moles)?
A) Increases
B) Decreases
C) Stays constant
D) Cannot be determined without values
E) Drops to zero
10. Which law results when temperature is held constant in the Combined Gas Law?
A) Charles’s Law
B) Boyle’s Law
C) Avogadro’s Law
D) Dalton’s Law
E) Gay-Lussac’s Law
11. Which law results when pressure is constant in the Combined Gas Law?
A) Boyle’s Law
B) Avogadro’s Law
C) Gay-Lussac’s Law
D) Charles’s Law
E) Ideal Gas Law
12. Which law results when volume is constant in the Combined Gas Law?
A) Dalton’s Law
B) Boyle’s Law
C) Gay-Lussac’s Law
D) Charles’s Law
E) None
13. A gas at 2 atm and 300 K has a volume of 5 L. What is the pressure if the volume becomes 10 L and the temperature becomes 600 K?
A) 2 atm
B) 4 atm
C) 1 atm
D) 0.5 atm
E) 3 atm
14. What happens to pressure if volume decreases and temperature increases simultaneously?
A) Pressure decreases
B) Pressure stays the same
C) Pressure increases
D) Pressure becomes zero
E) Pressure cannot change
15. Which of the following is not assumed in the Combined Gas Law?
A) Gas particles occupy negligible space
B) Gas molecules do not interact
C) The number of moles is constant
D) The gas is ideal
E) Gas temperature can be negative in Kelvin
16. Why must Kelvin be used for temperature in the Combined Gas Law?
A) Kelvin is easier to measure
B) Kelvin starts at absolute zero
C) Celsius gives smaller values
D) Kelvin is used for pressure
E) To match the volume unit
17. A sealed container shows pressure rising when heated. This illustrates:
A) Charles’s Law
B) Boyle’s Law
C) Combined Gas Law
D) Avogadro’s Law
E) Graham’s Law
18. In the Combined Gas Law equation, what happens if T₂ = 0 K?
A) Pressure increases
B) The equation is undefined
C) Volume increases
D) Gas becomes ideal
E) Pressure = 0
19. The Combined Gas Law does not apply accurately at:
A) Low pressure
B) High temperature
C) High pressure and low temperature
D) Constant volume
E) Constant temperature
20. What variable is missing from the Combined Gas Law that appears in the Ideal Gas Law?
A) Volume
B) Temperature
C) Pressure
D) Number of moles (n)
E) Gas constant (R)
Answers with Explanations
1. C – Pressure, volume, and temperature are related.
2. D – The formula is (P×V)/T=constant(P × V)/T = \text{constant}(P×V)/T=constant.
3. C – It combines Boyle’s, Charles’s, and Gay-Lussac’s laws.
4. D – The number of moles must stay constant.
5. B – The equation assumes no change in gas quantity.
6. B – Volume decreases when pressure increases at constant T and n.
7. C – Kelvin is the correct absolute scale for temperature.
8. C – Use the formula: (2×4)/300 = (P×V)/600 → V = 2 L.
9. D – Both variables change, so the effect on pressure is not certain without values.
10. B – Boyle’s Law (P × V = constant) assumes constant temperature.
11. D – Charles’s Law (V ∝ T) holds at constant pressure.
12. C – Gay-Lussac’s Law (P ∝ T) applies at constant volume.
13. C – (2×5)/300 = (P×10)/600 → P = 1 atm.
14. C – Lower volume and higher temperature → higher pressure.
15. E – Temperatures in Kelvin cannot be negative.
16. B – Kelvin starts at absolute zero, which avoids negative temps.
17. C – All three variables are involved → Combined Gas Law.
18. B – Division by zero is undefined (T₂ can’t be 0 K).
19. C – At high pressure/low temp, gases deviate from ideal behavior.
20. D – The number of moles n is included in the Ideal Gas Law but not in the Combined Gas Law.
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