The mass fractions of carbon and hydrogen in the hydrocarbon are 85.71% and 14.29%, respectively.

The mass fractions of carbon and hydrogen in the hydrocarbon are 85.71% and 14.29%, respectively. Give the molecular and structural formulas of a given substance if it is known that one of its molecules contains three carbon atoms.

Given:
C3Hx
ω (C in C3Hx) = 85.71%
ω (H in C3Hx) = 14.29%

To find:
C3Hx -?

Decision:
1) Mr (C3Hx) = N (C in C3Hx) * Ar (C) * 100% / ω (C in C3Hx) = 3 * 12 * 100% / 85.71% = 42.002;
2) x = (ω (H in C3Hx) * Mr (C3Hx)) / (Ar (H) * 100%) = (14.29% * 42.002) / (1 * 100%) = 6;
3) C3Hx – C3H6 – propene;

Answer: Unknown hydrocarbon – C3H6 – propene.