When C2H6(g) reacts with O2(g) according to the following reaction, 1.43×103 kJ of energy are evolved for each mole of C2H6(g) that reacts. Complete the following thermochemical equation.

2C2H6(g) + 7O2(g)>4CO2(g) + 6H2O(g) DeltaH = kJ

-2.86x10³ kJ

Explanation:

The enthalpy of a reaction (ΔH) is defined as the heat produced or consumed by a reaction. In the reaction:

2 C₂H₆(g) + 7 O₂(g) → 4 CO₂(g) + 6 H₂O(g)

The ΔH is the heat envolved in the reaction per 2 moles of C₂H₆. 1.43x10³ kJ are involved when 1 mole reacts. Thus, when 2 moles react, involved heat is:

1.43x10³ kJ ₓ 2 = 2.86x10³ kJ. As the reaction is a combustion reaction (Produce CO₂ and H₂O), the heat involved in the reaction is PRODUCED, that means ΔH is negative, -2.86x10³ kJ