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Question 3.77: Determine the formula, then the molar mass of each compound.......

Determine the formula, then the molar mass of each compound. Determine the mass of hydrogen in each formula. The mass of hydrogen divided by the molar mass of the compound (with the result multiplied by 100%) will give the mass percent hydrogen. Ranking, based on the percents, is easy.

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\begin{matrix} \text{Name} & \text{Chemical} &\text{Molar mass} & \text{Mass percent H} \\ & \text{formula} & \text{(g/mol)} & \text{[(mass H)/(molar mass)]}\times 100\% \\ \text{Ethane} & \text{C}_2\text{H}_6 & 30.07 & [(6\times 1.008)/(30.07)]\times 100\%=20.11\%\text{ H} \\ \text{Propane} & \text{C}_3\text{H}_8 & 44.09 & [(8\times 1.008)/(44.09)]\times 100\%=18.29\%\text{ H} \\ \text{Cetyl palmitate} & \text{C}_{32}\text{H}_{64}\text{O}_2 & 480.83 & [(64\times 1.008)/(480.83)]\times 100\%=13.42\%\text{ H} \\ \text{Ethanol} & \text{C}_2\text{H}_5\text{OH} & 46.07 & [(6\times 1.008)/(46.07)]\times 100\%=13.13\%\text{ H} \\ \text{Benzene} & \text{C}_6\text{H}_6 & 78.11 & [(6\times 1.008)/(78.11)]\times 100\%=7.743\%\text{ H}\end{matrix}

The hydrogen percentage decreases in the following order:
Ethane > Propane > Cetyl palmitate > Ethanol > Benzene

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