A volume of 0.285 L of a gas at STP weighs 0.537 g. Calculate the molar mass of the gas

(1)(0.285) = n(0.0821)(273).

.0036
is this correct?

3 answers

no. The number of moles may be .0036.

molmass=grams/numbermoles
so it would be
(1)(.0036)=n(.0821)(273)?
Do you know what a mole is?
You solve PV = nRT for n which gives moles. Then moles = grams/molar mass and solve for molar mass.