Thermochemical data for the dissolution of two ionic solids in water at 25 °C are…
CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
Thermochemical data for the dissolution of two ionic solids in water at 25 °C are shown below.
Salt
Lattice enthalpy, ΔHlattice (kJ mol−1)
Hydration enthalpy, ΔHhydr (kJ mol−1)
KCl
+715
–690
CaCl2
+2255
–2340
(The lattice enthalpy is defined as the enthalpy change for the formation of 1 mol of the solid from its gaseous ions.)
(a) Using the data above, calculate the enthalpy of solution, ΔHsoln, for each salt.
(b) Based on your calculations, identify which salt is expected to be more soluble in water at 25 °C and justify your choice.
(c) For the salt whose dissolution is endothermic, predict qualitatively how its solubility will change if the temperature is raised to 40 °C. Explain your reasoning.