posted by Mike .
Consider the dissolution of CaCl2.
CaCl2(s) Ca2+(aq) + 2 Cl-(aq) ÄH = -81.5 kJ
A 10.4-g sample of CaCl2 is dissolved in 102 g of water, with both substances at 25.0°C. Calculate the final temperature of the solution assuming no heat lost to the surroundings and assuming the solution has a specific heat capacity of 4.18 J/°C · g.
delta H for 10.4 g CaCl2 =
81.5 kJ/mol x (10.4/110.98) = about 8 kJ but you need to do it more accurtely.
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
8000J = 102g x 4.18 x (Tfinal-25). Solve for Tfinal.