Post on 29-Dec-2015
transcript
Solution Components
Solute – what is being dissolved
Solvent – what is doing the dissolving
May be combinations of gases, liquids, and solids
Suspensions
Particles of solute are too large to stay in solution and settle out unless constantly mixed
Colloids
Particles of solute are small enough to be kept moving by the motion of the solvent particles but big enough to scatter light
EX – fog, mayonnaise Tyndall effect
Electrolytes vs. Nonelectrolytes
Electrolytes dissociate in solution and conduct an electric current
Non-electrolytes do not
Factors Affecting the Rate of Dissolution
Increasing surface area
Agitating the solution (stirring)
Heating the solvent
Solubility
There is a limit to how much solute will dissolve in a given amount of solvent
As more solute is added, there is a greater likelihood that solute molecules/ions will collide and recrystalize
Solution equilibrium – the physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates
Unsaturated vs Saturated
A solution that contains the maximum amount of dissolved solute is said to be SATURATED
A solution that contains less solute than a saturated solution under the same conditions is said to be UNSATURATED
Supersaturated Solutions
A solution that contains more dissolved solute than a saturated solution contains under the same conditions is said to be SUPERSATURATED
Solubility Values
The amount of a substance required to form a saturated solution with a specific solvent at a given temperature
“Like Dissolves Like”
Polar solvents can dissolve ionic or polar compounds
Non-polar solvents can dissolve non-polar compounds
Depends on bonding and intermolecular forces between solvent and solute
Liquid Solutes & Solvents
Oil and water are said to be IMMISCIBLE because they cannot dissolve in each other
Liquids that can dissolve each other are said to be MISCIBLE (benzene/carbon tetrachloride or oil/gas)
Pressure Effects on Solubility
Effects mainly gasses
As pressure increases solubility increases
Henry’s Law – the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid
Temperature Effects on Solubility
In general, as temperature increases solubility of solids increase
As temperature increases solubility of gases decreases
Heats of Solution
Change in the amount of heat generated as a solute is SOLVATED (surrounded by solvent molecules)
If ΔH greater than start endothermic
If ΔH less than start exothermic