Cyclohexene, a hydrocarbon, has a molar mass of 82.1 g/mole. if the combustion of 0.8300 g cyclohexene produces 0.9102 g h2o and 2.668 g co2, what is the molecular formula of this compound?

Answer is: the molecular formula is C₆H₁₀.

Chemical reaction: C₆Hₓ + yO₂ → 6CO₂ + x/2H₂O.

m (H₂O) = 0.9102; mass of the water.

n (H₂O) = m (H₂O) : m (H₂O)

n (H₂O) = 0,9102 g : 18 g/mol

n (H₂O) = 0,0505 mol.

From chemical reaction: n (H) = 2 · n (H₂O).

n (H) = 0.101 mol.

m (CO₂) = 2.668 g; mass of carbon dioxide.

n (CO₂) = 2.668 g : 44 g/mol.

n (CO₂) = 0.0606 mol; amount of the substance.

n (CO₂) = n (C) = 0.0606 mol.

n (C) : n (H) = 0.606 mol : 0.101 mol.

n (C) : n (H) = 6 : 10; proportion of carbon and hydrogen atoms in cyclohexene.

The molecular formula will be C6H10.

Explanation;

Given dа ta:

mass of compound = 0.8300 g mass of H2O = 0.9102 g mass of CO2 = 2.668 g

Solution:

% of C = (mass of CO2/mass of compound) * (12/44) * 100

% of C = (2.66:0.8300) * (12/44) * 100 = 87.40 %

% of H = (mass of H2O/mass of compound) * (2/18) * 100

% of H = (0.910:0.8300) * (2/18) * 100 = 12.18 %

Niiw we calculate moles of C and H from % as follow

moles of C = 87.40/12 = 7.2 mol

moles of H = 12.18/1 = 12.18 mol

In we take atomic ratio

C : H

12.18/7.2 : 7.2/7.2

1.69 : 1

multiply atomic ratio by 3 to get whole no.

C : H = 3 (1.69:1) = 5 : 3

So empirical formula is C3H5.

Calculations of molecular formula:

empirical formula mass of C3H5 = 41

n = molar mass of compound / empirical formula mass

n = 82.1/41 = 2

Molecular mass = n * empirical formula = 2 * C3H5 = C6H10