A tank initially at a pressure of 670 atm contains 20 moles

A tank initially at a pressure of 6.70 atm contains 2.0 moles of oxygen gas at 25.0 degrees celsius. Its temperature is then increased to 45.0 degrees celsius, and an additional 10.0 moles of gas are added. What is the final pressure of the tank?

Solution

The only thing that remains constant throughout is the volume of the tank, and hence the volume occupied by gas.

PV = nRT in both conditions can be applied.

Now, V/R remains fixed throughout the process.

So, n1 x T1 / P1 = n2 x T2 / P2

=> 2 x (273+25) / 6.7 = 12 x (273 + 45) / P2

=> P2 = 42.9 atm