Carbon dioxide, formed during the complete combustion of 0.1 mol of alkane, when passed into an excess of lime water

Carbon dioxide, formed during the complete combustion of 0.1 mol of alkane, when passed into an excess of lime water, will give 60 g of a white precipitate. Determine the molecular formula of this hydrocarbon.

Given:
The general formula for alkanes is CnH2n + 2
n (CnH2n + 2) = 0.1 mol
m (sediment) = 60 g

To find:
CnH2n + 2 -?

Decision:
1) CnH2n + 2 + O2 -> CO2 ↑ + H2O;
CO2 + Ca (OH) 2 => CaCO3 ↓ + H2O;
2) M (CaCO3) = Mr (CaCO3) = Ar (Ca) * N (Ca) + Ar (C) * N (C) + Ar (O) * N (O) = 40 * 1 + 12 * 1 + 16 * 3 = 100 g / mol;
3) n (CaCO3) = m (CaCO3) / M (CaCO3) = 60/100 = 0.6 mol;
4) n (C) = n (CaCO3) = 0.6 mol;
5) N (C) = n (C) / n (CnH2n + 2) = 0.6 / 0.1 = 6;
6) Unknown substance – C6H14.

Answer: Unknown substance – C6H14.