Chemistry · THERMODYNAMICS

For most ionic compounds, the enthalpy of solution (\( \Delta_{\text{sol}} H^\ominus \)) is positive, yet they dissolve in water. Why does the solubility of most such salts increase with a rise in temperature?

1. Because hydration enthalpy becomes infinitely negative at elevated temperatures.
2. Because the dissolution is endothermic, and according to Le Chatelier's principle, an increase in temperature shifts the equilibrium towards dissolution.
3. Because lattice enthalpy decreases to zero at higher temperatures.
4. Because ionic radius of cations decreases upon heating, decreasing the hydration shell.