Chem 30 school question

Question

when 50.0 ml of 1 mol/liter agno3 and 50ml of 1 mol/litre Hcl are mixed in a calroimeter, the temperature rises by 8.1 celcius

determine the molar enthalpy change per mole of acid for the given reaction

Answer 1

Solve for ΔH in -n_AΔH = mc_wΔT where A is the moles of acid and we assume the solutions to have the density of water (1 g/ml) (100 grams total) and the specific heat of water: 4.184 J/mol K.

The mix is stoichiometric, so you don't have to worry about a limiting reactant and the enthalpy per mole of acid is the same as enthalpy per mole of acid.

Answer 2

The net ionic reaction is Ag¹⁺(aq) + Cl^1- (aq) → AgCl (s). The reaction involves 0.05 mol of Ag ions and 0.05 mol of Cl ions to give 0.05 mol of AgCl. To determine the molar enthalpy change per mole of acid, realize that the heat of reaction goes to increase the temperature of 100 g of water. The heat necessary to change the temperature of water by 8.1° is obtained from the relation Q = 4.182 J/g-C x 100 g x 8.1° = 3387.4 J.

As this is the energy produced by the production of 0.05 mole of AgCl, the energy produced by the production of one mole of AgCl is given by 3387.4 J /0.05 mol = 67748 J/mol which is the enthalpy change per mole of AgCl or per mole of acid. To 2 sig figs, this would be 68 kJ/mol.