Final answer:
The solubility of endothermic compounds like Mg(OH)2, ZnS, Ca3(PO4)2, and CaCO3 increases with temperature due to Le Châtelier's principle, while CuI and NiBr2's solubility remains unchanged with pressure increase or common ion effect.
Step-by-step explanation:
The solubility of compounds can be affected by changes in temperature, pressure, the presence of a common ion, or exposure to light. For substances like Mg(OH)2, ZnS, Ca3(PO4)2, and CaCO3, an increase in temperature typically results in increased solubility.
This is because the dissolution process for these compounds is endothermic, and according to Le Châtelier's principle, the system will react by shifting the equilibrium to the right to relieve the stress of added heat, which results in more solute dissolving.
On the other hand, for compounds such as CuI and NiBr2, the solubility remains unchanged under increased pressure or due to the common ion effect since these factors do not significantly affect the dissolution process of these particular compounds. The presence of a common ion usually decreases the solubility of a salt, due to a shift in equilibrium towards the reactants to counteract the increase in ion concentration, as seen in the common ion effect.