HCl (aq) + NaOH (aq) -> NaCl (aq) + H2O (l)

Question

Will the neutralisation reaction be endothermic or exothermic? Hint: think about the net ionic equation.

So, taking the hint, I got: OH- + H+ -> H2O

Not sure how that helps, and now I'm stuck; how would I figure out if this is endothermic or exothermic?

My teacher was also saying something about turning something reactive, stable. And then that would be an exothermic reaction because... (didn't catch the next part). I don't know if that's relevant or if it helps at all, but yeah.

On a side note and kind of irrelevant to this question (but still chemistry related), my teacher was saying something along the lines of, "higher enthalpy products require more energy; the reaction would be endothermic". I feel like I heard wrong; shouldn't the reaction be exothermic then?? Since more energy was used to make bonds resulting in more energy released..? If I did hear right, could you please explain?

Answer 1

I have looked all over the net and I can't find the value for delta H for H^+ + OH^- ==> H2O but I know it is exothermic. All neutralization reactions are exothermic; some more than others.

Answer 2

I remember this from last year - you should have a table of the heat of enthalpy somewhere in your book. From this you'll need to get the values of delta H (heat) of each mixture. The left side (HCl + NaOH) is the reaction and the right side is the result - you'll learn why later on. Calculate the total delta H of the reaction and subtract the total delta H of the product from it. If you get a positive value, it radiates heat which means it's exothermic. If it is negative, heat is needed to get a reaction so it is endothermic.