Question

Difficulty: MediumGeneral Gas Law, Ideal Gas Equation, and Molar Volume

A high-pressure diving cylinder contains 5.00 dm35.00\text{ dm}^3 of compressed air at a pressure of 3.00 atm3.00\text{ atm} and a temperature of 27C27^\circ\text{C}. If the air is expanded into a flexible chamber where the pressure drops to 1.50 atm1.50\text{ atm} and the temperature rises to 54C54^\circ\text{C}, what is the final volume of the gas?

  1. A
    20.00 dm320.00\text{ dm}^3
  2. 10.90 dm310.90\text{ dm}^3Answer
  3. C
    9.17 dm39.17\text{ dm}^3
  4. D
    2.73 dm32.73\text{ dm}^3

Answer

The final volume of the gas is 10.90 dm310.90\text{ dm}^3.
Applying the General Gas Law formula P1V1T1=P2V2T2\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} with temperatures converted to Kelvin (T1=300 KT_1 = 300\text{ K}, T2=327 KT_2 = 327\text{ K}) correctly yields V2=3.00×5.00×3271.50×300=10.90 dm3V_2 = \frac{3.00 \times 5.00 \times 327}{1.50 \times 300} = 10.90\text{ dm}^3.

Step-by-Step Solution

1
Convert initial and final temperatures from degrees Celsius to Kelvin.
T1=27C+273=300 KT_1 = 27^\circ\text{C} + 273 = 300\text{ K} and T2=54C+273=327 KT_2 = 54^\circ\text{C} + 273 = 327\text{ K}.
Gas laws strictly require absolute temperature in Kelvin for proportional relationships to hold true.
2
State the General Gas Law equation and rearrange for the final volume (V2V_2).
P1V1T1=P2V2T2    V2=P1V1T2P2T1\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \implies V_2 = \frac{P_1 V_1 T_2}{P_2 T_1}.
The equation relates changes in pressure, volume, and absolute temperature for a fixed mass of gas.
3
Substitute the given values into the rearranged equation and compute the result.
V2=3.00 atm×5.00 dm3×327 K1.50 atm×300 K=4905450=10.90 dm3V_2 = \frac{3.00\text{ atm} \times 5.00\text{ dm}^3 \times 327\text{ K}}{1.50\text{ atm} \times 300\text{ K}} = \frac{4905}{450} = 10.90\text{ dm}^3.
Simplifying the numerical expression yields the final expanded volume.

Key Concept

General Gas Law (Combined Gas Law) and Absolute Temperature Scale
Estimated Time:1m 30s
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