Answer to Question #73219 in General Chemistry for Joycelyn Jackson

Question

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The standard enthalpy of formation of solid barium oxide, BaO, is -553.5 kJ/mol, and the standard enthalpy of formation of barium peroxide, BaO2, is -643.3 kJ/ mol.

(a) Calculate the standard enthalpy change for the following reaction. Is the reaction exothermic or endothermic ?

2 BaO2(s) —> 2 BaO(s) + O 2(g)

(B) draw an energy level diagram that shows the relationship between the enthalpy change of the decomposition of BaO2 to BaO and O2 and enthalpies of formation of BaO2(s).

Answer 1

Solution
For the products: 2x(-553.5) kJ/mol
For the reactants: 2x(-643.3) kJ/mol
For the reaction: 2x(-553.5) - 2x(-643.3) = 179.6 kJ/mol. Endothermic!