If I make an ice pack with 750 mL of water, what mass of ammonium chloride must I include to get the temperature to drop from 20 degrees celsius to 5 degrees celsius. The heat of solution of the water and ammonium chloride is 14.8 kJ/mole. I just need help setting this problem up.

Answer 1

First you must determine how much heat must be removed to make that temperature transition.
q = [mass H2O x specific heat H2O x (Tfinal0Tinitial)].
q should be in J.

Then calculate mols NH4Cl needed to get that q.
14,800 J/mol x # mols = q(in J)
Then convert mols NH4Cl to grams.