S11E2 - Three Factors Affecting the Solubility of a Solution

There are 3 factors that must be considered when determining the solubility of a solution. They are:

1. Structure Effects
2. Pressure Effects
3. Temperature

Let's take a look at each of these factors in detail.

1. Structure Effects

   ➞ Structure Effects  =  "like dissolves like"

Solubility is favored when the solute and the solvent have similar properties. In other words:

- polar solutes dissolve in polar solvents.
- nonpolar solutes dissolve in nonpolar solvents.

ex:  vitamins A, D, E, and K are fat-soluble, while vitamins B and C are water-soluble.

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2. Pressure Effects

This only affects gas solubility in a solvent!

ex:  carbonation, CO₂(g), in a bottle of soda...

➞ To ensure a large amount of CO₂ is dissolved in water, soda is bottled at high pressures. "Fizzing" occurs as CO₂(g) molecules escape from the liquid solvent because they're no longer soluble at atmospheric pressure (1 atm).

Henry's Law

Henry's Law = the amount of gas dissolved in a solution is proportional to the pressure of the gas above the solution:

C = kP  ,  where k = constant

C = concentration of the dissolved gas
P = partial pressure of the gas solute above the solution

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3. Temperature Effects

We'll assume our solvent is H₂O and thus all solutions are "aqueous solutions."

Let's talk about the solubilities of solid, liquid, and gas solutes separately...

a. solid solute  (ex: sugar)

➞ most solids become more soluble as temperature increases.

b. liquid solute  (ex: ethanol)

➞ most liquids become more soluble as temperature increases.

c. gas solute  (ex: CO₂)

➞ most gas solutes become less soluble as temperature increases.
➞ Why?...

Because as the temperature of the solution increases, dissolved gas particles have a greater tendency to escape the liquid, thus decreasing their solubility in the solvent.

K.E. ∝ T

If the temperature increases, the kinetic energy of the moving gas particles also increases. More energy means greater tendency to escape the H₂O solvent.

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Next up in SECTION 11 - Solutions and Their Properties,

We'll talk about the Vapor Pressure of Solutions, Nonvolatile Solutes, and Raoult's Law.