Question

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

A sample of gas in a flexible container occupies a volume of 4.00 dm34.00\text{ dm}^3 at 27C27^\circ\text{C} and a pressure of 1.50 atm1.50\text{ atm}. What will be the volume of the gas if the temperature is increased to 127C127^\circ\text{C} and the pressure is reduced to 1.00 atm1.00\text{ atm}?

  1. A
    28.2 dm328.2\text{ dm}^3
  2. 8.00 dm38.00\text{ dm}^3Answer
  3. C
    4.50 dm34.50\text{ dm}^3
  4. D
    6.00 dm36.00\text{ dm}^3

Answer

The final volume of the gas is 8.00 dm38.00\text{ dm}^3.
Applying the General Gas Law P1V1T1=P2V2T2\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} requires converting all temperatures to Kelvin: T1=27+273=300 KT_1 = 27 + 273 = 300\text{ K} and T2=127+273=400 KT_2 = 127 + 273 = 400\text{ K}. Rearranging for V2V_2 gives V2=P1V1T2P2T1=1.50×4.00×4001.00×300=8.00 dm3V_2 = \frac{P_1 V_1 T_2}{P_2 T_1} = \frac{1.50 \times 4.00 \times 400}{1.00 \times 300} = 8.00\text{ dm}^3. Thus, the option stating 8.00 dm38.00\text{ dm}^3 is correct.

Step-by-Step Solution

1
Convert temperatures from degrees Celsius to Kelvin
T1=27+273=300 KT_1 = 27 + 273 = 300\text{ K} and T2=127+273=400 KT_2 = 127 + 273 = 400\text{ K}
Gas laws require absolute temperature units in Kelvin for linear proportional relationships.
2
State the General Gas Law equation and rearrange for final volume (V2V_2)
V2=P1V1T2P2T1V_2 = \frac{P_1 V_1 T_2}{P_2 T_1}
The General Gas Law relates pressure, volume, and temperature for a fixed amount of gas.
3
Substitute the given values into the rearranged equation
V2=1.50 atm×4.00 dm3×400 K1.00 atm×300 KV_2 = \frac{1.50\text{ atm} \times 4.00\text{ dm}^3 \times 400\text{ K}}{1.00\text{ atm} \times 300\text{ K}}
Plugging in P1=1.50 atmP_1 = 1.50\text{ atm}, V1=4.00 dm3V_1 = 4.00\text{ dm}^3, T1=300 KT_1 = 300\text{ K}, P2=1.00 atmP_2 = 1.00\text{ atm}, and T2=400 KT_2 = 400\text{ K}.
4
Evaluate the mathematical calculation
V2=2400300=8.00 dm3V_2 = \frac{2400}{300} = 8.00\text{ dm}^3
Simplifying the fraction gives the final gas volume.

Key Concept

General Gas Law (P1V1/T1=P2V2/T2P_1 V_1 / T_1 = P_2 V_2 / T_2)
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