posted by Pressure of gas .
A piston contains 1m^3 of helium at a temperature of 250 K and an absolute pressure of 1.0kPa. The following changes are made in sequence:
(a) First the volume of the piston is decreased to 0.2 m^3 while the temperature is kept constant, what is the pressure of the gas?
(b) Taking the gas after process (a) has been carried out. Now the volume of the gas is kept fixed at 0.2 m^3 but the temperature of the gas is raised to 500K. What does the pressure of the gas become?
(a) At constant T, P*V is constant.
(b) At constant V, P is proportional to (absolute) T. T goes from 250K to 500 K in this step.