Question

Difficulty: EasyGas Laws and the Ideal Gas Equation

A rigid steel container holds a fixed mass of gas at an initial pressure of 1.20×105 Pa1.20 \times 10^5\text{ Pa} and a temperature of 27C27^\circ\text{C}. If the temperature of the gas is increased to 127C127^\circ\text{C} while keeping its volume constant, what is the final pressure of the gas?

  1. 1.60×105 Pa1.60 \times 10^5\text{ Pa}Answer
  2. B
    5.64×105 Pa5.64 \times 10^5\text{ Pa}
  3. C
    0.90×105 Pa0.90 \times 10^5\text{ Pa}
  4. D
    4.44×105 Pa4.44 \times 10^5\text{ Pa}

Answer

The final pressure of the gas is 1.60×105 Pa1.60 \times 10^5\text{ Pa}.
According to Gay-Lussac's law, at constant volume, the pressure of a fixed mass of gas is directly proportional to its absolute temperature (P1/T1=P2/T2P_1/T_1 = P_2/T_2). Converting the temperatures to Kelvin gives T1=300 KT_1 = 300\text{ K} and T2=400 KT_2 = 400\text{ K}. Solving for P2P_2 yields P2=1.20×105 Pa×400300=1.60×105 PaP_2 = 1.20 \times 10^5\text{ Pa} \times \frac{400}{300} = 1.60 \times 10^5\text{ Pa}.

Step-by-Step Solution

1
Convert temperatures from Celsius to Kelvin
T1=27+273=300 KT_1 = 27 + 273 = 300\text{ K}, T2=127+273=400 KT_2 = 127 + 273 = 400\text{ K}
Gas laws require absolute temperature in Kelvin to maintain proportional relationships.
2
Apply Pressure Law (Gay-Lussac's Law) for constant volume
P1T1=P2T2    P2=P1×T2T1\frac{P_1}{T_1} = \frac{P_2}{T_2} \implies P_2 = P_1 \times \frac{T_2}{T_1}
For a fixed mass of gas at constant volume, pressure is directly proportional to absolute temperature.
3
Substitute the known values to calculate the final pressure
P2=(1.20×105 Pa)×400 K300 K=1.60×105 PaP_2 = (1.20 \times 10^5\text{ Pa}) \times \frac{400\text{ K}}{300\text{ K}} = 1.60 \times 10^5\text{ Pa}
Multiplying the initial pressure by the temperature expansion factor yields the final pressure.

Key Concept

Gay-Lussac's Law (Pressure Law)
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