a.
Vi antar att vi har 100g av ämnet.
\[\begin{aligned} m_\mathrm{C} &= 85,6\% \cdot 100\mathrm{g}=85,6\mathrm{g} \\ n_\mathrm{C} &= \frac {m_\mathrm{C}}{M_\mathrm{C}} = \frac {85,6\mathrm{g}}{12,01\frac {\mathrm{g}}{\mathrm{mol}}} = 7,12739384\mathrm{mol} \\ m_\mathrm{H} &= 14,4\% \cdot 100\mathrm{g} =14,4\mathrm{g} \\ n_\mathrm{H} &= \frac {m_\mathrm{H}}{M_\mathrm{H}} = \frac {14,4\mathrm{g}}{1,008\frac {\mathrm{g}}{\mathrm{mol}}} = 14,2857143\mathrm{mol}\end{aligned}\]
\[n_\mathrm{C}:n_\mathrm{H} ≈ 7:14 = 1:2\]
Den empiriska formeln måste vara CH2.
b.
\[\begin{aligned} M_\mathrm{faktisk} &= 70,1\mathrm{g/mol} \\ M_\mathrm{CH_2} &= (12,01 + 1,008 \cdot 2)\mathrm{g/mol} = 14,026\mathrm{g/mol} \\ \frac {M_\mathrm{faktisk}}{M_\mathrm{CH_2}} &= \frac {70,1\mathrm{g/mol}}{14,026\mathrm{g/mol}} = 4,99786112 ≈ 5\end{aligned}\]
Molekylformeln är (CH2)5 ⇔ C5H10.
