Nitrogen dioxide, NO2(g) (Delta. Hf = 33.84 kJ/mol), is decomposed according to the following reaction:

2 upper N upper O subscript 2 (g) right arrow upper N subscript 2 (g) plus 2 upper O subscript 2 (g).

What is the enthalpy change when 2.50 mol of nitrogen dioxide decomposes?
Use Delta H r x n equals the sum of delta H f of all the products minus the sum of delta H f of all the reactants..

13.5 kJ of energy released
13.5 kJ of energy absorbed
84.6 kJ of energy released
84.6 kJ of energy absorbed