Derive the formula for a hydrocarbon in which the mass fraction of carbon is 92.31%
| April 24, 2021 | education
Derive the formula for a hydrocarbon in which the mass fraction of carbon is 92.31%, hydrogen is 7.69%, and the density by air is 2.69.
Knowing the relative density D of organic matter in air (2.69), it is possible to calculate the molar mass of an unknown substance, since D is equal to the ratio of the molar mass of the desired substance to the molar mass of air (29 g / mol).
D = M / M (air) = 2.69
M = 2.69 * M (air) = 2.69 * 29 = 78 g / mol
The mass fraction of the element in the compound is calculated by the formula:
w (C) = n * A (C) / M = n * 12/78 = 0.9231.
n = 6
w (H) = m * A (H) / M = m * 1/78 = 0.0769.
m = 6
The formula for the desired organic substance is C6H6. This is an unsaturated hydrocarbon – benzene.
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