## Chemistry and Chemical Reactivity (9th Edition)

Atomic weights: $C: 12.011\ g/mol,\ H: 1.008\ g/mol$ Mass fractions of carbon: a) $\frac{12.011}{12.011+4\times1.008}\times100\%=74.9\%$ b) $\frac{2\times12.011}{2\times12.011+6\times1.008}\times100\%=79.9\%$ c) $\frac{3\times12.011}{3\times12.011+8\times1.008}\times100\%=81.7\%$ d) $\frac{4\times12.011}{4\times12.011+10\times1.008}\times100\%=82.7\%$