Need help with Chemistry problem. I need to calculate the molar enthaply (delta H).?

Question

A quantity of 25 mL 2.0 M NaOH is mixed with 25mL 2.0 M HCl, yielding water and sodium chloride. This is all of the infomation that the problem gives, how do I calculate the molar enthalpy. I am assuming the temperature is constant, but it doesn't even give a temperature, do I need one?

It says I must write the balanced net ionic equation, and the calculate the molar enthalpy of the reaction.

Can someone help me with this please?

Answer 1

The reaction between Hydrochloric acid and sodium hydroxide solutions:
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
where both HCl and NaOH are of concentration 1M.
Since the HCl and NaOH dissociate into ions in solution (before and after mixing the same), the ionic equation is:
H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) → Na+(aq) + Cl−(aq) + H2O(l)
And since the sodium and chloride ions are just spectator ions not involved in the reaction, the net equation becomes:
H+(aq) + OH−(aq) → H2O(l) : ΔH = −55.90 kJ mol−1
This illustrates why neutralization reactions are also referred to as water forming reactions. Of course the sodium and chloride ions are still in solution but they are just spectators. Of course you need to find from your book the ΔH = −55.90 kJ mol−1 of the water forming reactions (at 1M).