Why does the temperature of solution change marginally upon addition of sodium chloride to water?

1 Answer
Feb 15, 2016

Because the dissolution of sodium chloride is ONLY slightly endothermic.


#NaCl(s) + excess H_2O rarr Na^(+)(aq) + Cl^(-)(aq)#

This reaction is very slightly endothermic. The energy required to breakup the ionic lattice is ALMOST balanced by the formation of ion-dipole bonds between the ion and the solvent water molecules. For other salts, for instance sodium hydroxide, or ammonium chloride, dissolution in water is strongly exothermic (#NaOH#) or strongly endothermic (#NH_4Cl)#.