A given mass of a real gas in a rigid container is heated from 400 to 1200K. Which of the following responses best describes what will happen to the pressure of the gas?
a. the pressure will increase by a factor of 3
b. the pressure will increase by a factor of less than 3
c. the pressue will decrease by a factor of 3
d. the pressure will increase by a factor of greater than 3
e. the pressure will remain the same.