unit 2: solutions chemistry 12. properties of solutions review solutions

Unit 2:Solutions

Chemistry 12

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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)

http://en.wikipedia.org/wiki/Image:SaltInWaterSolutionLiquid.jpg


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 issurrounded by solvent molecules arranged in a specific manner)

1. Solvent-solvent interactions2. Solute-solute interactions3. Solvent-solute interactions

NOT A CHEMICAL REACTION!!!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

StrongElectrolyte

Non-Electrolyte

Completely ionized in

water

- +

salt

- +

sugar

Not ionized in water

- +

acetic acid

WeakElectrolyte

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.


SolubilitySATURATED SOLUTIONno more solute dissolves at a certain temp

UNSATURATED SOLUTIONmore 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 Solubility CurveCurve

shows the dependence of solubility on temperature

X-axis: temperatureY-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

unit 2: solutions chemistry 12. properties of solutions review solutions

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