Question

which of the following increases solubility of solids in liquids?
a increasing temperature
b decreasing surface area
c decreasing agitation
d lowering temperature

Explanation:

• Increasing temperature: Generally, for solids dissolving in liquids (except for some exceptions like \(Ca(OH)_2\)), when the temperature is increased, the kinetic energy of the solvent molecules increases. This allows the solvent molecules to more effectively break the intermolecular forces in the solid (such as ionic or covalent bonds in ionic or molecular solids respectively) and surround the solute particles, thus increasing solubility.
• Decreasing surface area: Decreasing the surface area of the solid means there is less contact between the solid and the liquid. According to the dissolution process (which is a surface - phenomenon to some extent), less contact leads to a slower dissolution rate (not an increase in solubility. Solubility is a measure of the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature, and surface area affects the rate of dissolution, not the solubility limit).
• Decreasing agitation: Agitation (stirring) affects the rate at which the solute dissolves (by distributing the dissolved solute away from the surface of the undissolved solid more quickly). It does not affect the solubility (the maximum amount of solute that can dissolve). A lower rate of agitation just means it will take longer for the system to reach the solubility limit (saturation point), but the solubility value itself is unchanged.
• Lowering temperature: As mentioned before (for most solids), lowering the temperature decreases the kinetic energy of the solvent molecules. So, they are less able to break the intermolecular forces in the solid and solvate the solute particles. This leads to a decrease in solubility (again, with exceptions like \(Ca(OH)_2\), but the general trend is for an increase in solubility with increasing temperature for most solids).

Answer:

A. Increasing temperature