Answer
$178amu$
Work Step by Step
From ideal gas law
$n=\frac{PV}{RT}$
We plug in the known values to obtain:
$n=\frac{\frac{985}{760}\times 0.345}{0.08206\times 421}=0.01294mol$
Now we can find the molar mass as
$Molar \space mass =\frac{2.30g}{0.01294mol}=178\frac{g}{mol}$
Hence the molecular weight is $178amu$
