What is the molar mass of 81.50 g of gas exerting a pressure of 1.75 atm on the walls of a pressure or 1.27 atm on the walls of 4.92 l container of 307 k?

Here, we may apply the equation of state for an ideal gas, which is:
PV = nRT
We may substitute the number of moles, n, with:
moles = mass / molecular mass

PV = mRT/Mr

Mr = (mRT)/PV
Substituting the values:

Mr = (81.5 * 0.082 * 307) / (1.75 * 4.92)
Mr = 238.3

The molar mass of the gas is 238.3 grams per mole.