Post on 06-Jan-2018
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Unit 2:Solutions
Chemistry 12
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Properties of Solutions Review
Solutions
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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
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Solute(Salt)
Solvent (Water)
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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
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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
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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!!!
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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.
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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
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“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
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Everyday Solvation• Soap/DetergentSoap/Detergent
– polar “head” with long non-polar “tail”
– dissolves non-polar grease in polar water
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• 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.
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Solvation
StrongElectrolyte
Non-Electrolyte
Completely ionized in
water
- +
salt
- +
sugar
Not ionized in water
- +
acetic acid
WeakElectrolyte
Incompletely ionized in
water
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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.
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SolubilitySATURATED SOLUTIONno more solute dissolves at a certain temp
UNSATURATED SOLUTIONmore solute dissolves
SUPERSATURATED SOLUTION
becomes unstable, crystals form
concentration
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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
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Solubility
• Solubility Solubility CurveCurve
shows the dependence of solubility on temperature
X-axis: temperatureY-axis: grams solute per 100mL water
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• Anything that falls below the line is UNSATURATED
• Anything above the line is SUPERSATURATED
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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.
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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