A Big heat/energy question.?

Question

How much heat energy is given out when 300ml of 0.1 M NaOH solution is reacted with sufficient HCl solution.

NaOH(aq) + HCl(aq) -> NaCl(aq) + H2O(aq) ?H= -56.2kJ/mol NaOH

And assuming that the volume of the solution after reaction is 600 mL, with mass 600g and the initial temperature of the solution was 25°C, and also assuming that the heat capacity of the solution is the same as water's = 4.184 J/g/K. What is the final temperature of the solution after the reaction?

This is a nasty one. I'd like to see the work.

Thankyou very much, hfshaw.

Answer 1

This is not "nasty"; it's really pretty straightforward.

300 ml of a 0.1M solution of NaOH contains 0.3*0.1 = 0.03 moles of NaOH. The neutralization reaction of one mole of NaOH liberates -56.2kJ of energy, so the neutralization of 0.03 moles of NaOH liberates 3% of this: 0.03*56.2kJ = 1686 J.

If all this energy goes into heating 600 gm of a solution that has a heat capacity of 4.184 J/(gm*K), the temperature of that solution would increase by:

delta-T = (1686 J)/[600 gm * 4.184 J/(gm*K)] = 0.672 K

If the original solution had a temperature of 25 C, and no heat is lost, the final solution would have a temperature of 25.672 C.

Answer 2

I try not to think of thermochemisry questions when I don't have to.