An old rusting iron tank containing a mystery gas was found near the Alberta/NWT border by a highway crew constructing a new exit ramp. The crew foreman felt it was necessary to determine what the gas was in tank before releasing it into the air or shipping the gas to the proper disposal authorities. The following information was obtained to help determine what the gas was.

Tank material: iron
Pressure of the gas inside the tank: 350.1 kPa
Temperature of the gas inside the tank: 11°C
Tank Volume: 1500 L
Tank mass with mystery gas: 1265.77 kg
Tank mass once the gas was removed: 1250.00 kg

a. Calculate the molar mass, of the gas inside the tank.

b. What is the mystery gas in the tank and provide the chemical formula?