Question

Upon combustion, a 10.582 g sample of a C, H, O compound produced 26.976 g CO2 and 6.894 g H20. What is the mass of oxygen in the sample? A) 2.839 g 0 B) 7.743 g 0 C) 2.456 g 0 D) 8.134 g 0

Answer 1

To solve this, we would need to calculate the moles of CO2 and H2O produced in the combustion.

Mass of CO2 = 26.976 g

Molar mass of CO2 = 44.01 g/ mol

Moles of CO2 = mass / molar mass = 26.976 g/ 44.01 g/mol = 0.613 mol

Mass of H2O = 6.894 g

Molar mass of H2O = 18.02 g /mol

Moles of H2O = 6.894 g/ 18.02 g/mol = 0.383 mol

1 mole of CO2 has 1 mole of carbon. 0.613 mole of CO2 is produced from the combustion of 0.613 mole of carbon. So the moles of carbon in the compound is 0.613 mol.

1 mole of H2O has 2 moles of Hydrogen. So 0.383 mole of H2O will be produced from 2 x 0.383 = 0.766 mole of hydrogen. This means there are 0.766 mole of hydrogen in the compound.

Mass of Carbon in compound = moles x molar mass = 0.613 mol x 12.01 g/mol = 7.36 g

Mass of Hydrogen in the compound = moles x molar mass = 0.766 mol x 1.01 g/mol = 0.77 g

Mass of the compound = 10.582 g

Mass of oxygen = mass of the compound - mass of Carbon - mass of Hydrogen = 10.582 g - 7.36 g - 0.77 g = 2.45 g

Correct answer is option C (2.456 g)