Which statements correctly describe factors affecting solubility?

• A. Temperature increases solubility of all solutes.
• B. Pressure has no effect on solubility.
• C. Temperature increases solubility for solids and decreases for gases; Pressure increases solubility as pressure increases.
• D. Only temperature matters; pressure never affects solubility.

Answer: (C)

Understanding how solubility changes with temperature and pressure depends on what is dissolving and where. For solids dissolving in liquids, heating usually makes solubility go up because the added thermal energy helps break apart the solid’s lattice and stabilizes the dissolved ions or molecules. For gases dissolved in liquids, increasing temperature tends to push the gas out of solution because the dissolved gas is expelled more readily as the system gains kinetic energy.

Pressure mainly affects gases: increasing external pressure pushes more gas into the liquid, so solubility rises with pressure in a manner described by Henry’s law. For solids, changing pressure at ordinary conditions has little effect on how much of the solid dissolves.

So the statement that temperature raises solubility for solids but lowers it for gases, and that solubility of gases increases with pressure, captures these general trends. The other ideas—such as solubility increasing for all solutes with temperature, or pressure having no effect, or that only temperature matters—don’t fit these observed patterns.