1. Find the values for the enthalpy changes of formation of NaOH(aq), HCl(aq), K

Question

1. Find the values for the enthalpy changes of formation of NaOH(aq), HCl(aq), KOH(s), and KOH(aq) in an appropriate reference work

2. Write balanced chemical equations corresponding to the values found in answer to Question 1.

3. The enthalpy change for any reaction can be obtained by subtracting the sum of the enthalpy changes of formation of the reactants from the sum of the enthalpy changes of formation of the products. Use this method to obtain the value of DeltaHneut for the reaction of NaOH(aq) and HCl(aq) and the value of the enthalpy change of solution for KOH.

Explanation / Answer

1. HNaOH = -112.23 kcal/mol; HKOH = -115 kcal/mol

HHCl = -40.02 kcal/mol; HKOH(s) = -102.02 kcal/mol

2. 2Na(s) + H2O(l) ------> 2NaOH(aq) + H2(g)

H3O+(aq) + 3Cl-(aq) ---------> HCl(aq) + H2O(l)

2K(s) + H2O(l) ------> 2KOH(aq) + H2(g)

2K(s) + H2 + O2 ------> 2KOH(s)

3. NaOH + HCl --------> NaCl + H2O HNaCl = -98.23 kcal/mol ; HH2O = -68.31 kcal/mol

Hr = (-98.23 + (-68.31)) - (-112.23 + (-40.02)) = -14.29 kcal/mol

2K(s) + H2O(l) ------> 2KOH(aq) + H2(g) HK = 0; HH2 = 0

Hr = (-115 + 0) - (-68.31 + 0) = -46.69 kcal/mol

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