If a gas has a pressure of 560 torr at 25C, at what temperature, in celsius, will it have a pressure of 430 torr?

Answer 1

This is a classic combined gas law problem. If the number of moles is kept constant, an ideal gas follows the relationship

P₁V₁/T₁=P₂V₂/T₂

In this case, we are left to assume that the volume is kept constant, so V₁=V₂ and they cancel. This gives us

P₁/T₁=P₂/T₂

The only thing we have to be careful of is that the temperature must be absolute (in kelvins) for all of the gas laws.

Solving for T₂ = P₂T₁/P₁

Then, just convert the temperature back to ^oC from kelvins.