Problem 4

Calculate the mass of ethane, C2H6, which must be burned to produce 100 kJ of heat.

2 CzH6 (9) + 7 02 (9) - --> 4CO2 (g) + 6 H2O (1) AH = - 3120 kJ

1.93 g

Explanation:

We are given;

The chemical equation;

2C₂H₆ (g) + 7O₂ (g) → 4CO₂ (g) + 6H₂O (l) ΔH = - 3120 kJ

We are required to calculate the mass of ethane that would produce 100 kJ of heat.

From the equation given; 2 moles of ethane burns to produce 3120 Kilo joules of heat Therefore;

Number of moles that will produce 100 kJ will be;

= (2 * 100 kJ) : 3120 kJ)

= 0.0641 moles

But, molar mass of ethane is 30.07 g/mol

Therefore;

Mass of ethane = 0.0641 moles * 30.07 g/mol

= 1.927 g

= 1.93 g

Thus, the mass of ethane that would produce 100 kJ of heat is 1.93 g