Question

What is the % C by mass in aspirin?

Answer 1

To get the percent by mass of Carbon in a compound like aspirin, divide the mass of carbon by the molecular mass of aspirin then multiply it by 100%.

$C_9H_8O_4=180.15g/mol$

$\%C=[\frac{(9)(12.01g/mol}{180.15g/mol}]\times100=60\%$