What is the mass of carbon in 500. g of octane?

The answer is: the mass of carbon is 420.6 grams.

m(C₈H₁₈) = 500 g; mass of octane.

M(C₈H₁₈) = 114.22 g/mol; molar mass of octane.

n(C₈H₁₈) = m(C₈H₁₈) ÷ M(C₈H₁₈).

n(C₈H₁₈) = 500 g ÷ 114.22 g/mol.

n(C₈H₁₈) = 4.38 mol; amount of octane.

In one molecule of octane, there are eight carbon atoms:

n(C) = 8 · n(C₈H₁₈).

n(C) = 8 · 4.38 mol.

n(C) = 35.02 mol; amount of carbon.

m(C) = 35.02 mol · 12.01 g/mol.

m(C) = 420.6 g; mass of carbone.