According to Henry's Law, at a constant temperature the amount of a gas dissolved in a solvent is directly proportional to its partial pressure when it is in equilibrium with its liquid phase.
When an ionic solid dissolves, ions leave the solid and become dispersed in the solvent. This solution can be classified as saturated, unsaturated or supersaturated.
Concept #1: Saturated, Unsaturated and Supersaturated Solutions.
In a hypothetical solution 100 mL of water can dissolve up to 100 g of solute. In a SATURATED solution the water has reached its maximum amount of dissolve solute.
In an UNSATURATED solution additional amounts of solute can be further dissolved in the solvent.
In a SUPERSATURATED solution the solvent has dissolved beyond its maximum solubility.
Example #1: Caffeine is about 10 times as soluble in warm water as in cold water. A student puts a hot-water extract caffeine into an ice bath, and some caffeine crystallizes. What is the identity of the solution before it’s been placed in an ice bath?
d) Not enough information to answer the question.
Concept #2: Understanding Henry's Law
Henry's Law relates the solubility of a gas over a solution based on the factors of temperature, volume and pressure.
Example #2: Henry’s Law Constant for nitrogen in water is 1.67 x 10-4 M•atm-1. If a closed canister contains 113 ppb nitrogen, what would be its pressure in atm?
As the temperature of the solution increases more and more gas molecules will exit the solvent.
Practice: In general, as the temperature increases, the solubility of gas in a given liquid ________________, and the solubility of most solids in a given liquid ________________.
a. Increases, increases
b. increases, decreases
c. decreases, increases
d. decreases, decreases
Practice: At a partial pressure of acetylene 1.35 atm, 1.21 moles of it dissolves in 1.05 L of acetonitrile. If the partial pressure of acetylene in acetone is increased to 12.0 atm, then what is its solubility?