Question

4.8 Quantitative Analysis A 1.052 g sample of an unknown compound, composed only of carbon and hydrogen produced 3.19 g of Co, and 1.63 g of H.O in a combustion analysis. What is the mass percent composition of hydrogen of the unknown compound? • Round to one decimal place. Provide your answer below:

Answer 1

Number of moles of H2O = mass of H2O / molar mass H2O

= 1.63/18

= 9.056*10^-2

Since 1 mol of H2O has 2 mol of H

Number of moles of H = 2*9.056*10^-2 = 0.1811

Mass of H = moles of H * molar mass of H

= 0.1811 mol * 1 g/mol

= 0.1811 g

Mass % of H = mass of H * 100 / mass of compound

= 0.1811 * 100 / 1.052

= 17.2 %

Answer: 17.2 %