Question

Calculate the heat of reaction, AHrxn, for the reaction between hydrogen sulfide and oxygen to form sulfur dioxide and water.

(∆H°f(H₂S(g)) = -20.2 kJ/mol, ∆H° f(SO₂(g)) = -296.9 kJ/mol and ∆H°f(H₂O(I)) = - 285.8 kJ/mol).

Answer 1

To find the heat of reaction for the formation of sulfur dioxide and water from hydrogen sulfide and oxygen, standard enthalpy of formation values are used, yielding an exothermic reaction with ΔHrxn of -1125 kJ.

Step-by-step explanation:

To calculate the heat of reaction, ΔHrxn, for the reaction of hydrogen sulfide (H2S) and oxygen (O2) to form sulfur dioxide (SO2) and water (H2O), we must use the standard enthalpy of formation values provided and apply Hess's law. The balanced chemical equation for the reaction is:

2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(l)

The enthalpy change for the reaction, ΔHrxn, is calculated with the formula:

ΔHrxn = [ΣΔH°f(products)] - [ΣΔH°f(reactants)]

Substituting the standard enthalpy of formation values:

ΔHrxn = [(2 mol × -296.9 kJ/mol) + (2 mol × -285.8 kJ/mol)] - [(2 mol × -20.2 kJ/mol) + (3 mol × 0 kJ/mol)]

ΔHrxn = [-593.8 kJ - 571.6 kJ] - [-40.4 kJ]

ΔHrxn = -1165.4 kJ + 40.4 kJ

ΔHrxn = -1125 kJ

Therefore, the heat of reaction is -1125 kJ, indicating that the reaction is exothermic.