Question 5.4.1: Calculate enthalpy change for a chemical reaction. When CO r......
Calculate enthalpy change for a chemical reaction.
When CO reacts with NO according to the following reaction, 373 kJ of energy is evolved for each mole of CO that reacts. Use this information to calculate the enthalpy change for the following reaction.
2 CO(g) + 2 NO(g) → 2 CO_{2}(g) + N_{2}(g) ∆H_{rxn} = ?
You are asked to calculate the enthalpy change for a given reaction.
You are given the amount of energy released when a given amount of reactant is consumed.
Energy is evolved in this reaction, so the sign of ∆H_{rxn} is negative. The equation shows the reaction of 2 mol of CO, so the energy change for the reaction is
∆H_{rxn} = 2 mol CO × \frac{-373\text{ J}}{1\text{ mol CO}} = –746 kJ
Is your answer reasonable? The energy change should be negative because the reaction gives off energy. The amount of energy released is twice that given in the problem because of the stoichiometry of the chemical equation.