Answer to Question #308431 in General Chemistry for Krix

Question

Percent Composition and Empirical Formula

1. Phosphoric acid (H3PO4) is a colorless, syrupy liquid used in detergents, fertilizers, toothpastes,

and in carbonated beverages for a “tangy” flavor. Calculate the percent composition by mass of H, P,

and O in this compound.

2. Propane is hydrocarbon, a compound composed only of carbon and hydrogen. It is 81.82%

carbon and 18.18% hydrogen. What is the empirical formula?

Answer 1

1. Molecular mass of H₃PO₄ = 3×1+31+64=98

% mass of H = $\frac{3}{98}= 3.06$ %

% mass of P = $\frac{31}{98}= 31.63$ %

% mass of O = $\frac{64}{98}= 65.306$ %

2.

18.18 % of H present in 81.82 % of C

18.18 g of H present in 81.82 g of C

Mole of H present $\frac{18.18}{18.18}= 18$mole

Mole of C =6.81

Emprical formula = CH₃