Unit 2: Solutions Chemistry 12

Properties of Solutions Review Solutions

Definitions Solution – a homogeneous mixture Solute – substance being dissolved Solvent – the component present in the greatest amount Aqueous Solution – Solution which has water for the solvent

Solute (Salt) Solvent (Water)

Types of Solutions Listed as solute-solvent [Page 238] –Gas/Gas: Air –Gas/Liquid: Carbonated drinks –Gas/Solid: Hydrogen in platinum –Liquid/Gas: Water vapor in air –Liquid/Liquid: Alcohol in water –Liquid/Solid: Mercury in Silver –Solid/Gas: Mothballs in the air –Solid/Liquid: Sugar in water –Solid/Solid: Alloys

How much solute is there in the solution? Concentrated Solution – higher proportion of solute to solvent than a dilute solution Diluted Solution – has a lower proportion of solute to solvent than a concentrated solution

3 Steps to Solvation Solvation –Solvation – the process of dissolving (the process in which an ion or molecule is surrounded by solvent molecules arranged in a specific manner) 1.Solvent-solvent interactions 2.Solute-solute interactions 3.Solvent-solute interactions NOT A CHEMICAL REACTION!!!

Solvation Consider NaCl (solute) dissolving in water (solvent). Water molecules orient themselves on the NaCl crystals. H-bonds between the water molecules have to be broken. NaCl dissociates into Na+ and Cl-. Ion-dipole forces form between the Na+ and the negative end of the water dipole. Similar ion-dipole interactions form between the Cl- and the positive end of the water dipole.

Polarity Degree of polarity is very important when dealing with aqueous solutions. Ex. Water –The OH bonds in water are polar –The O is slightly negative and will therefore cluster around positively charged molecules –The H is slightly positive and will cluster around negatively charged molecules

“Like Dissolves Like” A non-polar solute dissolves in a non-polar solvent A polar solute dissolves in a polar solvent A polar solute will not dissolve in a non-polar solvent A non-polar solute will not dissolve in a polar solvent

Everyday Solvation Soap/DetergentSoap/Detergent –polar “head” with long non- polar “tail” –dissolves non-polar grease in polar water

An electrolyte is a substance that, when dissolved in water, gives a solution that can conduct electricity A non-electrolyte does not conduct electricity when dissolved in water.

Solvation Strong Electrolyte Non- Electrolyte Completely ionized in water - + salt - + sugar Not ionized in water - + acetic acid Weak Electrolyte Incompletely ionized in water

Solubility The amount of solute that can be dissolved in a given amount of a saturated solution at a fixed temperature is the solubility of the solute in the solvent.

Solubility SATURATED SOLUTION no more solute dissolves at a certain temp UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration

Solubility SolubilitySolubility –maximum grams of solute that will dissolve in 100 g of solvent at a given temperature –varies with temperature –based on a saturated solution

Solubility Solubility CurveSolubility Curve shows the dependence of solubility on temperature X-axis: temperature Y-axis: grams solute per 100mL water

Anything that falls below the line is UNSATURATED Anything above the line is SUPERSATURATED

Solubility Solids are more soluble at...Solids are more soluble at... –high temperatures. Gases are more soluble at...Gases are more soluble at... - low temperatures & high pressures.

Can they mix?? Two liquids are said to be miscible if they are completely soluble in each other in all portions –Ex. ethanol and water In contrast, immiscible liquids do not mix significantly. - Ex. gasoline and water