Chem help! when 10.7g of solid ammonium chloride, NH4Cl is dissolved in 100ml of water the temp. drops from

when 10.7g of solid ammonium chloride, NH4Cl is dissolved in 100ml of water the temp. drops from 23.4° C to 16.4° C.
a) write the equation for dissolving the solid
b) find the heat of solution for NH4Cl

a) NH4Cl(s) --> NH4+(aq) + Cl-(aq)

b) heat lost by water = q = m c (T2-T1) = 100 g X 4.184 J/gC X (16.4 - 23.4 C) = -2929 J

Heat lost by H2O = - heat gained by NH4Cl on dissolving

So, dissolving absorbed 2929 J /10.7 g X 53.49 g/mol = 1.46X10^4 J/mol = 14.6 kJ/mol