Why is it thermodynamically possible for some ionic solids to dissolve even though the process is endothermic?

Spontaneity ...

There are two components which together decide whether a procedure is unconstrained or not: enthalpy change (ΔH) and entropy change (ΔS). Procedures which are unconstrained move from a higher vitality to a lower vitality and hinted at by the Gibbs free vitality.

ΔG = ΔH - TΔS

A negative ΔG shows an unconstrained procedure. Regardless of whether the enthalpy change is certain the entropy change can likewise be sure, which influence the estimation of ΔG to negative, demonstrating an unconstrained procedure. This makes sense since in the broke down state, where a substance is part separated into particles, the quantity of microstates will be more prominent (expanding entropy).