Elemental Composition of a Binary Mixture - Calculating % mass?

Question

A white powder, consisting of a simple mixture of tartaric acid (C4H6O6) and citric acid (C6H8O7) was analyzed to determine the elemental composition. Combustion of a 548.0-mg sample produced 682.3 mg of CO2 and 200.3 mg of H2O.

Use atomic masses: C 12.011; H 1.00794; O 15.9994.


Calculate the % carbon, by mass, in the sample.
Calculate the % hydrogen, by mass, in the sample.
Calculate the % oxygen, by mass, in the sample.
Calculate the % citric acid, by mass, in the sample.

Answer 1

31%

7.34 %

61.66 %

54 %