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.