A 6.789 g sample of a hydrocarbon, upon combustion analysis, yielded 6.527 grams of water. What is the percent, by mass, of hydrogen in the hydrocarbon?

Question

Quizplus · Accepted Answer

To find the percent by mass of hydrogen, first calculate the mass of hydrogen in the water produced. Water (H2O) has a molar mass of 18.015 g/mol, with hydrogen contributing 2.016 g/mol. The mass of hydrogen in 6.527 g of water is (2.016/18.015) * 6.527 g = 0.730 g. The percent by mass of hydrogen in the hydrocarbon is (0.730 g / 6.789 g) * 100% = 10.76%.

A 6789 G Sample of a Hydrocarbon, Upon Combustion Analysis, Yielded