Given the following information below, use Hess’s Law to calculate the enthalpy

ID: 590167 • Letter: G

Question

Given the following information below, use Hess’s Law to calculate the enthalpy of formation for sodium oxide:

Na (s) + HCl (l) à NaCl (aq) + ½ H2 (g) HRx = -393.1 kJ/mol

Na2O (s) + 2 HCl (l) à 2 NaCl (aq) + H2O HRx = -675.2 kJ/mol

H2 (g) + ½ O2 (g) à H2O (g) HRx = -288.1 kJ/mol

2 Na (s) + ½ O2 (g) à Na2O (s) HRx = __________ kJ/mol

Calculated Heat of Reaction is....?

(Put your answer in 4 significant figures)

Lets number the reaction as 1, 2, 3, 4 from top to bottom

required reaction should be written in terms of other reaction

This is Hess Law

required reaction can be written as:

reaction 4 = +2 * (reaction 1) -1 * (reaction 2) +1 * (reaction 3)

So, deltaHo rxn for required reaction will be:

deltaHo rxn = +2 * deltaHo rxn(reaction 1) -1 * deltaHo rxn(reaction 2) +1 * deltaHo rxn(reaction 3)

= +2 * (-393.1) -1 * (-675.2) +1 * (-288.1)

= -399.1 KJ/mol

Answer: -399.1 KJ/mol

Feel free to comment below if you have any doubts or if this answer do not work. I will edit it if you let me know

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