Question

Calculate the standard enthalpy change for the reaction between calcium oxide (CaO) and water (H2O) to form calcium hydroxide (Ca(OH)2), given that all species are in their standard state and that the balanced chemical equation is:CaO(s) + H2O(l) → Ca(OH)2(s)The standard enthalpies of formation of CaO(s), H2O(l) and Ca(OH)2(s) are -635.1 kJ/mol, -285.8 kJ/mol, and -986.2 kJ/mol respectively.

Answer 1

To calculate the standard enthalpy change for the reaction, we can use the following formula:H_reaction =  H_f products  -  H_f reactants where H_reaction is the standard enthalpy change for the reaction, H_f products  is the sum of the standard enthalpies of formation of the products, and H_f reactants  is the sum of the standard enthalpies of formation of the reactants.For this reaction, we have:H_f CaO  = -635.1 kJ/molH_f H2O  = -285.8 kJ/molH_f Ca OH 2  = -986.2 kJ/molNow, we can plug these values into the formula:H_reaction = [H_f Ca OH 2 ] - [H_f CaO  + H_f H2O ]H_reaction =  -986.2 kJ/mol  -  -635.1 kJ/mol + -285.8 kJ/mol H_reaction =  -986.2 kJ/mol  -  -920.9 kJ/mol H_reaction = -65.3 kJ/molSo, the standard enthalpy change for the reaction between calcium oxide and water to form calcium hydroxide is -65.3 kJ/mol.