The nuclide 38cl decays by beta emission with a half life of 40min. A sample of .40 m of H38cl is placed in a 6.24 liter container. After 80 min the pressure is 1650 mmHg. What is temperature of container?

I have tried calculating the decay rate of the 38cl and then plugging into the formula pv -net but I do not get the answer, 300 k. Any help would be great.