Question

Hydrogen reacts with chlorine to form hydrogen chloride (HCl (g), Delta.Hf = –92.3 kJ/mol) according to the reaction below.

Upper H subscript 2 (g) plus upper C l subscript 2 (g) right arrow 2 upper H upper C l (g).

Which statement is correct?
Use Delta H r x n equals the sum of delta H f of all the products minus the sum of delta H f of all the reactants..
The enthalpy of the reaction is –184.6 kJ, and the reaction is exothermic.
The enthalpy of the reaction is –184.6 kJ, and the reaction is endothermic.
The enthalpy of the reaction is 184.6 kJ, and the reaction is endothermic.
The enthalpy of the reaction is 184.6 kJ, and the reaction is exothermic.

Answer 1

Use ΔHrxn = ΣΔHf(products) − ΣΔHf(reactants).

ΔHrxn = 2(−92.3 kJ/mol) − [0 + 0] = −184.6 kJ, so the reaction releases heat and is exothermic.