Describe the standard enthalpy of formation of the aqueous

Question

When 1.3584g of sodium acetate trihydrate was mixed into the 100.0cm³ of 0.2000 M HCl (aq) at 25 ⁰Cin a solution calorimeter, its temperature fell by 0.397⁰C on account of the reaction:

H₃O⁺ (aq) +NaCH₃CO₂ . 3H₂O (s) -->Na⁺ (aq) + CH₃COOH (aq) + 4 H₂O(l).

Describe the standard enthalpy of formation of the aqueous sodium cation. The standard enthalpy of formation of sodium acetate trihydrate is-1064kJ/mol. The heat capacity of the calorimeter is 91.0 J/K and the heat capacity density of the acid solution is 4.144J/Kcm.