# The hydrogen vapor density of the hydrocarbon is 39. Find the molecular formula if the mass

The hydrogen vapor density of the hydrocarbon is 39. Find the molecular formula if the mass fractions of the elements are: carbon = 92.3%, hydrogen = 7.7%

Let’s write down the data on the condition of the problem:
1. Given: CxNu – hydrocarbon;
D (H2) = 39;
M (H2) = 2 g / mol;
W (C) = 92.3%
W (H) = 7.7%
Determine the molecular formula.
2. Calculate the molar mass:
M (CxHy) = M (H2) * D (H2) = 2 * 39 = 78 g / mol.
3. Find the number of moles of carbon, hydrogen:
Y (C) = m / M = 92.3 / 12 = 7.7;
Y (H) = m / M = 7.7 / 1 = 7.7.
4. Ratio: X: Y = 7, 7: 7, 7 = 1: 1;
Simplest formula: CH
Molecular Formula: C6H6;
M (C6H6) = 78 g / mol.
Answer: C6H6 – benzene belongs to the class of arenes.

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