Solubility factors: For dissolution of a nonvolatile solute in a liquid solvent, which parameter typically has the least (often negligible) effect on solubility under ordinary conditions?

Introduction / Context:When designing separation and formulation processes (e.g., crystallisation, extraction, and drug formulation), it is important to know which variables strongly influence solubility and which do not. For solids or liquids dissolving in liquids, some variables dominate while others have very little effect.

Given Data / Assumptions:

• Solute is a solid or a nonvolatile liquid.
• Solvent is a liquid (e.g., water or an organic solvent).
• Ordinary pressure ranges near 1 atm are considered.

Concept / Approach:For solid–liquid and liquid–liquid solubility, temperature can dramatically change solubility (endothermic dissolution generally increases with temperature). Chemical nature of the solute and solvent (polarity, hydrogen bonding, “like dissolves like”) is decisive. Pressure has minimal effect on condensed phases because liquids and solids are nearly incompressible, so small pressure changes do not appreciably alter chemical potentials or activities.

Step-by-Step Solution:

Verification / Alternative check:Contrast with gas solubility in liquids, where pressure matters greatly (Henry’s law). This highlights why the answer differs for gas–liquid systems.

Why Other Options Are Wrong:

• Temperature: Strong effect, widely used to tune solubility in industry.
• Nature of solute: Functional groups and lattice energies matter significantly.
• Nature of solvent: Polarity and interactions dominate solvation.

Common Pitfalls:Generalising Henry’s law (gas–liquid) to solid–liquid systems. Also, assuming pressure always matters because it affects boiling points; that does not imply a strong effect on solubility of condensed phases.

Final Answer:Pressure