Given the following salts and the corresponding enthalpy, predict whether the temperature will decrease or increase when the salt dissolves in water.

Question

Given the following salts and the corresponding enthalpy, predict whether the temperature will decrease or increase when the salt dissolves in water.

Ammonium Chloride (ΔHsol = +14.7 kJ/mol)

Answer 1

If the ∆Hsoln is positive (+) this tells us heat is absorbed by the system and removed from the surroundings, so the temperature will decrease.

If the ∆Hsoln is negative (-), this tells us heat is liberated by the system to the surroundings and the temperature will increase.

So for ammonium chloride, the ∆Hsoln is positive meaning the temperature will decrease when it dissolves in water.