Which alkane has the molecular formula C3H8?

The alkane with the molecular formula C3H8 is propane. Alkanes are saturated hydrocarbons, meaning they only contain single bonds between carbon atoms. The general formula for alkanes is CnH2n+2, where 'n' represents the number of carbon atoms in the molecule.

In the case of propane, there are three carbon atoms (C3) and using the formula, we can calculate the hydrogen required:

H = 2(3) + 2 = 8.

This confirms that propane, with three carbons and eight hydrogens, fits the molecular formula C3H8. The other options represent different hydrocarbons: methane has one carbon (C1H4), butane has four carbons (C4H10), and pentane has five carbons (C5H12), which means they do not match the molecular formula provided in the question.