[chsteven]

Hi! I need help getting started on this problem:

A 1.5.2L tank of Nz at20.4 psi and 13.2L tank of Oz at22.4pst
are connected together. When the tanks are connected and cooled to 145 K, the
partial pressure of Nz is 4.5 psi. Determine the original temperature, in K, of the
Nz tank before it was connected to the other tank.

[rabolisk]

PV = nRT is your friend here. Just watch out the unusual unit of psi. Remember that PV = nRT always works for any ideal gas, regardless of whether there is another ideal gas present in the same mixture. Think about what happens when tanks are "connected".