How to find molar mass of a gas by being given density and given temperature and pressure?

To identify the contents of an unknown cylinder of gas, a sample was collected and found to have a density of 5.380 g/L at 15 degree C and 736 mm Hg pressure. What is the molar mass of the gas? I want to say use molar volume of a gas which is 22.4 L/mol to give you g/mol, but I thought that it could only be used... show more To identify the contents of an unknown cylinder of gas, a sample was collected and found to have a density of 5.380 g/L at 15 degree C and 736 mm Hg pressure. What is the molar mass of the gas?
I want to say use molar volume of a gas which is 22.4 L/mol to give you g/mol, but I thought that it could only be used at STP.
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