solutions, acids, and bases parts of a solution solute the substance that is dissolved into the...
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Solutions, Acids, and Bases
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.
Dissolving
Three ways to dissolve a solute in a solvent:
1. Dissociation
2. Dispersion
3. Ionization
1. Dissociation
The process in which an ionic compound separates into ions in a solution. (physical change)
Example: salt in water
2. Dispersion
Breaking the solute into small pieces and spreading throughout the solvent.
Ex. Sugar in waterPhysical change
3. Ionization
The process in which neutral molecules lose or gain electrons.
Chemical changeEx: HCl in water
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
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
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
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.
Other factors:
2nd : Powdering the solute.
Increases the surface area
3rd : Heating the solution.
Speeds up the molecules
Concentration
ConcentratedA large amount
of solute dissolved in a solvent
DiluteA little bit of
solute dissolved in a solvent
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.
Supersaturation example:
Sodium acetate in water.
Used in commercial hand warmers.
Page 692 Q1 - 3
Insoluble
A substance that will NOT dissolve in water.
“Like dissolves like”
Nonpolar solvents will dissolve nonpolar solutes.
examples: benzene & acetone Polar solvents will dissolve polar solutes
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.
Acids
Very important chemicals in everyday life processes.
Properties of acids:
1. Sour taste (never taste a chemical)
2. All contain hydrogen ( which turn into hydronium ions H3O+)
3. Also called “proton donors”
4. React with active metals to produce hydrogen gas. (exp. 21)
Zn + 2HCl ZnCl2 + H2
Indicators
Chemicals used to identify acids and bases by changing color.
ACIDS:
A. Litmus paper (blue to red)
B. Phenolphthalein (colorless)
C. Methyl Orange (orange to red)
D. Bromothymol Blue (changes to yellow)
Common acids
Sulfuric (H2SO4) used in car batteries
Nitric (HNO3) also fertilizers
Hydrochloric (HCl) stomach acid Carbonic (H2CO3) carbonated drinks
Acetic (HC2H3O2) vinegar
Bases
Also very important in everyday processes.
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
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
Solutions of acids and bases
pH scale (page 704) 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.
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.
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.
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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