Charles' law is a special case of the ideal gas law where the pressure of a gas is constant. Charles' law states the volume is proportional to the absolute temperature of a gas at constant pressure. This example problem shows how to use Charles' law to solve a gas law problem.
A 600 mL sample of nitrogen is heated from 27 °C to 77 °C at constant pressure. What is the final volume?
The first step to solving gas law problems should be converting all temperatures to absolute temperatures. This is the most common place mistakes are made in this type of homework problem.
T K = 273 + °C
Ti = initial temperature = 27 °C
Ti K = 273 + 27
Ti K = 300 K
Tf = final temperature = 77 °C
Tf K = 273 + 77
Tf K = 350 K
The next step is to use Charles' law to find the final volume. Charles' law is expressed as:
Vi/Ti = Vf/Tf
Vi and Ti is the initial volume and temperature
Vf and Tf is the final volume and temperature
Solve the equation for Vf:
Vf = ViTf/Ti
Enter the known values and solve for Vf.
Vf = (600 mL)(350 K)/(300 K)
Vf = 700 mL
The final volume after heating will be 700 mL.