reactions, confused

Question

A chemist measures the energy change during the following reaction:

2NH3(g) --> N2(g) + 3H2(g) DeltaH: 160.kJ

Use the information to answer the following questions.

1. Is the reaction endo- or exo- thermic?
2. Suppose 24.7g of NH3 react. Will heat be released or absorbed?
3. If you said heat will be released or absorbed in the second part of this question, calculate how much heat will be released or absorbed. Be sure your answer has the correct number of significant digits.

Answer 1

As the delta H is positive is positive, the reaction is endothermic. The 160. kj is not specified per mole; so, the 160. kj is for the reaction of 2 moles of ammonia. 24.7g of ammonia corresponds to 1.45 moles of ammonia. The heat absorbed is 1.45/2 x 160. kj. or 116. kj.

Answer 2

1) Since ΔH is positive, the reaction is endothermic.

2) Because it's endothermic, then heat will be absorbed.

3)

(160. kJ/2 mol NH₃) (1 mol NH₃/17.0 g NH₃) 24.7 g NH₃ = 232.5 = 233 kJ