Complete combustion of the hydrocarbon produced 27 g of water and 33.6 liters of CO2.

| March 27, 2021 | education

Complete combustion of the hydrocarbon produced 27 g of water and 33.6 liters of CO2. The relative density of the hydrocarbon with respect to argon is 1.05. Establish its molecular formula.

Let’s represent the hydrocarbon formula in the form of CxHy, then the equation of its combustion can be written as follows:
CxHy + O2 = CO2 + H2O.
Let’s find the molar mass of an unknown substance through the density:
M (CxHy) = M (Ar) • D (Ar) = 40 • 1.05 = 42 g / mol.
The number of moles of carbon dioxide and water, respectively, will be equal:
n (CO2) = V: Vm = 33.6: 22.4 = 1.5 mol.
n (H2O) = m: M = 27/18 = 1.5 mol.
We get the ratio:
n (СО2) = n (C),
n (H2O) = n (H2),
the ratio in the hydrocarbon will be CxH2x.
We get the equation:
12x + 2x = 42.
x = 3.
Then the true formula C3H6 is propene.



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