Question

Predict whether the following reactions will be exothermic or endothermic.

Answer 1

Answer:

A. N₂(g) + 3H₂(g) -----> 2NH₃    exothermic

B. S(g) + O₂(g) --------> SO₂(g)    exothermic

C. 2H₂O(g) --------> 2H₂(g) + O₂(g) endothermic

D. 2F(g) ---------> F₂(g) exothermic

Explanation:

The question says predict not calculate. So you have to use your chemistry knowledge, experience and intuition.

A. N₂(g) + 3H₂(g) -----> 2NH₃    is exothermic because the Haber process gives out energy

B. S(g) + O₂(g) --------> SO₂(g)    is exothermic because it is a combustion. The majority, if not all, combustion give out energy.

C. 2H₂O(g) --------> 2H₂(g) + O₂(g) is endothermic because it is the reverse reaction of the combustion of hydrogen. If the reverse reaction is exothermic then the forward reaction is endothermic  

D. 2F(g) ---------> F₂(g) is exothermic because the backward reaction is endothermic. Atomisation is always an endothermic reaction so the forward reaction is exothermic