Question

Determine the standard enthalpy change for the reaction between calcium oxide and hydrochloric acid, given the following information:CaO(s) + 2HCl(aq) → CaCl2(aq) + H2O(l)∆Hf° CaCl2(aq) = -795.7 kJ/mol∆Hf° H2O(l) = -285.8 kJ/mol∆Hc° = -1922.6 kJ/mol

Answer 1

To determine the standard enthalpy change for the reaction between calcium oxide and hydrochloric acid, we can use Hess's Law. According to Hess's Law, the total enthalpy change for a reaction is the sum of the enthalpy changes for each step in the reaction.In this case, we have the following steps:1. Formation of CaCl2 aq  from its elements:    Ca s  + Cl2 g   CaCl2 aq    Hf CaCl2 aq  = -795.7 kJ/mol2. Formation of H2O l  from its elements:   H2 g  + 1/2 O2 g   H2O l    Hf H2O l  = -285.8 kJ/mol3. Combustion of CaO s :   CaO s  + H2 g  + Cl2 g   CaCl2 aq  + H2O l    Hc = -1922.6 kJ/molNow, we can use Hess's Law to find the enthalpy change for the reaction between calcium oxide and hydrochloric acid:Hrxn = Hf CaCl2 aq  + Hf H2O l  - HcHrxn =  -795.7 kJ/mol  +  -285.8 kJ/mol  -  -1922.6 kJ/mol Hrxn = -1081.5 kJ/mol + 1922.6 kJ/molHrxn = 841.1 kJ/molSo, the standard enthalpy change for the reaction between calcium oxide and hydrochloric acid is 841.1 kJ/mol.