Question #a206f

1 Answer
Aug 8, 2015

The answer is c. remains unchanged


Think about what you're dealing with here.

Temperature is actually a measure of average kinetic energy, which means that constant temperature implies a constant average kinetic energy.

In your particular case, you know that volume decreases. Assuming that the number of moles of gas is constant, this change in volume, provided that temperature is kept constant as well, can only lead to an Increase in pressure - this is known as Boyle's Law.

However, this increase in pressure cannot be attributed to an increase in the average energy of the molecules of gas, since temperature is kept constant.

The reason pressure increases is that the frequency of the collissions between the gas particles and between the gas particles and the container walls increases.

In other words, the molecules have the same average kinetic energy, but they hit the wall of the container more frequently, which implies an overall increase in pressure.

So, when you keep temperature constant, you keep average kinetic energy constant. Any other change in pressure or volume is unrelated to the average kinetic energy of the molecules.