Question

For which compound does 0.256 mole weigh 12.8 g?

Answer 1

Number of moles = $\frac{mass (g)}{Molar mass}$
so to calculate molar mass (Molecular weight of compound):
Molecular weight = $\frac{mass (g)}{number of moles}$
            = $\frac{12.8 g}{0.256 mole}$ = 50 g / mole
Now we calculate molecular weight of each compound in choices:
a) C₂H₄O = 44
b) CO₂ = 44
c) CH₃Cl = 50.4 ALMOST 50  so this is the correct answer
d) C₂H₆ = 30