An alkane weighing 0.88 grams has a volume of 0.448 liters. What is the molecular weight and formula?

General formula for an unknown alkane: CnH2n + 2.

Let’s find the amount of the substance of the unknown alkane:

v (CnH2n + 2) = V (CnH2n + 2) / Vm = 0.448 / 22.4 = 0.02 (mol).

Thus, the molar mass of the unknown alkane is:

M (CnH2n + 2) = m (CnH2n + 2) / v (CnH2n + 2) = 0.88 / 0.02 = 44 (g / mol), which numerically corresponds to a molecular weight of 44 (amu).

Let’s compose and solve the equation:

12 * n + 1 * 2n + 2 = 44,

14n = 42,

n = 3, whence the alkane formula: C3H8 (propane).