The combustion of some 2.2 g alkane produced 3.36 liters of CO2. Determine the alkane formula.

1. Let us write the equation of combustion of alkanes in general form:

CxH2x + 2 + (1.5x + 0.5) O2 → xCO2 + (x + 1) H2O;

2.Calculate the chemical amount of carbon dioxide:

n (CO2) = V (CO2): Vm = 3.36: 22.4 = 0.15 mol;

3. determine the amount of alkane: n (CxH2x + 2) = m (CxH2x + 2): M (CxH2x + 2);

M (CxH2x + 2) = 12 * x + 2 * x + 2 = 14 * x + 2 g / mol;

n (CxH2x + 2) = 2.2: (14 * x + 2) mol;

4.we express the amount of unknown alkane in terms of CO2 and find x:

n (CxH2x + 2) = n (CO2): x = 0.15: x;

2.2: (14 * x + 2) = 0.15: x;

2.2 * x = 0.15 * (14 * x + 2);

2.2 * x – 2.1 * x = 0.3;

0.1 * x = 0.3;

x = 3.

Answer: С3H8.