Establish the formula of hydrocarbons if, when burning 0.2 m of a substance, 10.8 g of water

Establish the formula of hydrocarbons if, when burning 0.2 m of a substance, 10.8 g of water and 17.92 of carbon dioxide were formed.

1.we make the equation:

CxHy + O2 → xCO2 + 0.5yH2O;

2.According to the equation, the amount of CO2 is x times greater than the consumed amount of hydrocarbon:

n (CO2) = x * n (CxHy) = 0.2 * x;

3.Calculate the chemical amount of carbon dioxide from its mass:

n (CO2) = m (CO2): M (CO2);

M (CO2) = 12 + 2 * 16 = 44 g / mol;

n (CO2) = 17.92: 44 = 0.4 mol;

4.from n (CO2) = 0.2 * x = 0.4 mol, we express x:

x = 0.4: 0.2 = 2;

5.find the amount of water according to the data from the problem statement:

n (H2O) = m (H2O): M (H2O);

M (H2O) = 2 + 16 = 18 g / mol;

n (H2O) = 10.8: 18 = 0.6 mol;

6. according to the reaction, we express the amount of water from the known amount of hydrocarbon and equate to the found one:

n (H2O) = 0.5 * y * n (CxHy) = 0.2 * 0.5 * y = 0.6 mol;

y = 0.6: 0.1 = 6;

7.we substitute the found values ​​instead of the indices x, y and write the formula:

CxHy = C2H6.

Answer: C2H6.