Combined gas law

Question

can Someone help me solve my last chem problem

A 12 liter tank contains 7 moles of oxygen. The pressure in the tank is 660 kPa at 25 C. If this oxygen tank were to leak, and lose 3 moles of O2 gas and the temperature now drops to 13 C, what would be the new pressure in the tank? Assume the volume of the tank stays the same at 12 liters.

Answer 1

P₁V₁/n₁T₁ = P₂V₂/n₂T₂ which is a modification of the combined gas law (which doesn't generally include n, moles). Since V is constant, it drops out of the equation. Rearrange the equation to solve for P₂ :

P₂ = P₁n₂T₂/n₁T₁

Convert the temps from ^oC to K, put in the values, and calculate P₂