Question

When 20.8 g of calcium chloride, CaCl2, was dissolved in water in a calorimeter, the temperature rose from 25.0°C to 37.1°C. If the heat capacity of the solution and the calorimeter is 1258 J/°C, what is the enthalpy change when 1 mol of calcium chloride dissolves in water? The solution process is the following.
CaCl2(s) Ca2+(aq) + 2 Cl-(aq

Answer 1

1. Convert 20.8 g CaCl2 to moles (Diveide by the formula mass of CaCl2).
2. The heat given off is:
∆H(sln) = (1258 J/°C)(37.1°C - 25.0°C)
3. Divide the answer in step #2 by the answer in #1 to get the joules/mole. This value is negative since the heat is given off.