Answer
$92.24$%
Work Step by Step
Calculate the total mass of carbon in the compound. The calculate the molar mass of the entire compound. Divide the total mass of carbon by the total molar mass of the compound. Then, multiply by 100% to determine the percent composition by mass.
Molar Mass of C:
$2(12.0107g/mol)=24.0214g/mol$
Molar Mass of C2H2:
$2(12.0107g/mol)+2(1.0079g/mol)=26.0372g/mol.$
% $C=(24.02g/mol÷26.04g/mol)×100$%
$=92.24$%
