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Is there a LIMIT to how much solute can dissolve into the solvent?. Solutions. Homogeneous Mixtures. Solution :. Solvent: substance present in a Greater (Larger) amount Solute: substance that is present in a lesser (Smaller) amount . “Likes dissolve likes”.
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Is there a LIMIT to how much solute can dissolve into the solvent?
Solutions Homogeneous Mixtures
Solution : • Solvent: substance present in a Greater (Larger) amount • Solute: substance that is present in a lesser (Smaller) amount
“Likes dissolve likes” Polar dissolves in polar Sugar and water Nonpolar dissolves in non polar crayons and oil
CONCENTRATION Molarity (M or mol/L) • Mole fraction ( cor mol/ mol total) • Molality (m or mol/Kg solvent) • Mass percent (% or g/ g total)
Definitions Solutions can be classified as saturated or unsaturated. A saturated solution contains the maximum quantity of solute that dissolves at that temperature.
Solvation Process D6 c20 • Solvation: The attaching of solvent particles to solute particles.
SATURATED SOLUTIONS Solubility: Maximum amount of solute per 100 g solvent
Dissolving Effects: c34 • Saturated Solution- maximum amount of solute in solution • Any extra solute added just sits on bottom. • Unsaturated- less than max. solute than then can be dissolve. • Supersaturated- A solution containing more solute than normal for a given temperature. • Must heat a saturated solution up. Then return it to room temperature.
For a Supersaturated solution, when more solute is added, the extra solute will settle to the bottom
Supersaturated Sodium Acetate • One application of a supersaturated solution is the sodium acetate “heat pack.” • Sodium acetate has an ENDOthermic heat of solution.
Solubility Curves How much LiCl will dissolve into 100 ml of water at a temperature of 20 C? How much KCl will dissolve into 500 ml of water at a temperature of 80 C? How much RbCl will fall out of solution if 200 ml of solution is cooled from a temperature of 80 C to 20 C?
Dissolving Effects • Solubility- the quantity of solute that will dissolve in 100 g of solvent at a set temperature • If solution is holding the MAX. Amount of solute called saturated • Solidionic compounds: more in with higher temperature • Gases: More in at lower temperatures
SOLIDS GAS
Dissolving Gases & Pressure Gas solubility can be changed by both the temperature and PRESSURE. When the can of soda is opened the pressure (Pgas) drops and causes the solubility to decrease.
Henry’s Law Gas solubility (mol/L) = Sg Sg = kH • Pgas kH = Henry’s law constants for O2 = 1.66 x 10-6 M/mmHg When Pgas increases, solubility increases.
Henry’s Law What is the concentration of oxygen in fresh water when the air pressure is 1 atm? Sg = kH • Pgas kHfor O2 = 1.66 x 10-6 M/mmHg O2 = 21% so 0.21(760 torr) = Pgas Sg= 1.66 x 10-6 M/mmHg • 160 torr = 2.66 x 10-4 M What is the concentration of oxygen in milligrams/ liter? O2 = 8.5 mg/L