Ideal Gas Example Problem - Constant Volume
Worked Chemistry Problems
The ideal gas law applies to real gases at low temperatures.
Paul Taylor, Getty Images
by Todd Helmenstine

Updated November 28, 2014

Question The temperature of a sample of an ideal gas confined in a 2.0 L container was raised from 27 °C to 77 °C. If the initial pressure of the gas was 1200 mm Hg, what was the final pressure of the gas?

Solution

Step 1

Convert temperatures from Celsius to Kelvin

K = °C + 273

Initial temperature (T_{i} ): 27 °C

K = 27 + 273 K = 300 Kelvin T_{i} = 300 K

Final temperature (T_{f} ): 77 °C

K = 77 + 273 K = 350 Kelvin T_{f} = 350 K

Step 2

Using the ideal gas relationship for constant volume , solve for the final pressure (P_{f} )

P_{i} / T_{i} = P_{f} / T_{f}

solve for P_{f} :

P_{f} = (P_{i} x T_{f} ) / T_{i} P_{f} = (1200 mm Hg x 350 K) / 300 K P_{f} = 420000 / 300 P_{f} = 1400 mm Hg

Answer

The final pressure of the gas is 1400 mm Hg.