When a 8.45-mg sample of a compound containing carbon is burned completely, 18.1 mg of carbon dioxide is produced. What is the mass percentage of carbon in the compound?

Answer 1

mass C = 18.1 mg CO2 x (atomic mass C/molar mass CO2) = ?
%C = (Mass C/mass sample)*100 = ?

Answer 2

Assuming all of the carbon from compound is converted to carbon dioxide the mass amount of carbon => (12/44)100% = 27.27% of CO2 produced. From this, the mass of carbon in the 18.1mg of CO2 => 18.1(.2727)mg = 4.94mg carbon. Therefore, the %C in sample = (4.94/8.45)100% = 58.41% by wt.