Solutions, Acids, and Bases

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Solutions, Acids, and Bases

• Chapter 16

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Parts of a solution

• Solute
• The substance that is dissolved into the
  solution.
• examples
• Sugar in kool-aid
• Salt in salt water
• CO2 in pop

• Solvent
• The substance that does the dissolving in a
  solution.
• examples
• Most common is water.

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Dissolving

• Three ways to dissolve a solute in a solvent
• Dissociation
• Dispersion
• Ionization

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1. Dissociation

• The process in which an ionic compound separates
  into ions in a solution. (physical change)
• Example salt in water

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2. Dispersion

• Breaking the solute into small pieces and
  spreading throughout the solvent.
• Ex. Sugar in water
• Physical change

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3. Ionization

• The process in which neutral molecules lose or
  gain electrons.
• Chemical change
• Ex HCl in water page 230

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Conductivity

• Many solutions can conduct an electric current if
  electrolytes are present. (ions)
• Electrolytes substances that will conduct an
  electric current when dissolved. Ex. NaCl, KCl,
  MgBr2

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Freezing Point Depression

• Lowering the freezing point of water by the
  addition of a solute
• ex. salt.
• Used on icy roads in winter
• Ice-cream

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Boiling point elevation

• The addition of a solute to a liquid solvent will
  usually raise the boiling point of the solvent.
• Adding salt to boil water when cooking

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Heat of Solution

• A measure of the amount of energy either absorbed
  or released when a solute dissolves in a solvent.
• Can be endothermic or exothermic.

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Rate of Solution

• Speed at which solute dissolves in a solvent.
• 1st Stirring the solution. Helps to move the
  solute particles away from the solid solute.

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Other factors

• 2nd Powdering the solute.
• Increases the surface area

• 3rd Heating the solution.
• Speeds up the molecules

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Concentration

• Concentrated
• A large amount of solute dissolved in a solvent

• Dilute
• A little bit of solute dissolved in a solvent

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Saturation

• A solution that contains all the solute it can
  possibly hold at a given temperature is said to
  be saturated.
• Unsaturated contains less solute than it can
  possibly hold
• Supersaturated a solution that holds more
  solute than it should at a given temperature.

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Supersaturation example

• Sodium acetate in water.
• Used in commercial hand warmers.

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Insoluble

• A substance that will NOT dissolve in water.

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Like dissolves like

• Nonpolar solvents will dissolve nonpolar solutes.
• examples benzene acetone
• Polar solvents will dissolve polar solutes

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2 factors that affect solubility

• 1.Temperature
• Increase in temp generally increases solubility
  of a solid in a liquid
• Increase in temp decreases solubility of a gas in
  a liquid.

• 2. Pressure
• Usually has little, if any, effect on solid and
  liquid solutes.
• Increase in pressure increases the solubility of
  a gas in a liquid.

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Specific concentration

• Can be defined as percent by volume or percent by
  mass
• Example 3 hydrogen peroxide or 25 fruit juice.

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MOLARITY
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Acids

• Very important chemicals in everyday life
  processes.

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Properties of acids

• Sour taste (never taste a chemical)
• All contain hydrogen
• Also called proton donors
• React with active metals to produce hydrogen gas.
  (exp. 21)
• Zn 2HCl ZnCl2 H2

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Indicators

• Chemicals used to identify acids and bases by
  changing color.
• ACIDS
• Litmus paper (blue to red)
• Phenolphthalein (colorless)
• Methyl Orange (orange to red)
• Bromothymol Blue (changes to yellow)

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Common acids

• Sulfuric (H2SO4) used in car batteries
• Nitric (HNO3) also fertilizers
• Hydrochloric (HCl) stomach acid
• Carbonic (H2CO3) carbonated drinks
• Acetic (HC2H3O2) vinegar

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Bases

• Also very important in everyday processes.

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Properties of Bases

• Taste bitter feel slippery
• Contain hydroxide (OH) ions.
• Known as proton acceptors
• Phenolphthalein turns bright pink
• Red litmus paper turns blue
• Bromothymol blue turns blue
• Methyl orange turns yellow

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Common bases

• Sodium hydroxide NaOH making soap drain
  cleaners
• Potassium hydroxide KOH battery electrolyte
• Calcium hydroxide Ca(OH)2 making plaster and
  drywall
• Magnesium hydroxide Mg(OH)2antacids

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Solutions of acids and bases

• pH scale (page 247)
• A numerical scale developed to measure the
  relative strengths of acids and bases
• Ranges from 0 to 14
• 0 is the strongest acid
• 14 is the strongest base.

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What happens when an acid and a base combine?

• Always forms water and a salt.
• Salt ionic compound formed when a positive ion
  of a base combines with a negative ion of an
  acid.
• Neutralization.
• These are double replacement reactions. Examples
  (on board)

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What determines if an acid is classified as
strong or weak?

• Which is stronger? 1 M acetic acid or 1M
  hydrochloric acid?
• Strength is determined by how well the acid or
  base dissociates into solution.
• Strong acids and strong bases are good
  electrolytes.

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Buffers

• A mixture of a weak acid or weak base with its
  salt.
• Resists large changes in pH.
• Examples
• Bicarbonate ions in your blood stream.

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Assignment

• Pages 257-258
• 1-10, 11, 13, 16, 20, 22, 23, 24, 27, 30, 31, 32