A student dissolved 10.5 g of NH4Cl in 40 mL of water. The temperature of the water changed from 22.5oC to 5.1oC. Calculate the enthalpy of hydration of ammonium chloride in J/mol.

Answer 1

q in joules = mass H2O x specific heat x (Tfinal=Tinitial)
That gives you J in 10.5 grams. Convert the 10.5 g to mols and that will be J/? moles. Convert to 1 mols.