Solutions, Acids, and Bases
Download
Report
Transcript Solutions, Acids, and Bases
Solutions, Acids,
and Bases
Chapter 7 & 8
Parts of a solution
Solute
The substance that
is dissolved into the
solution.
examples:
• Sugar in kool-aid
• Salt in salt water
• CO2 in soda
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 water
Physical change
3. Ionization
The
process in which neutral
molecules lose or gain
electrons.
Chemical change
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
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.
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
Concentrated
Dilute
A large
A little
amount
of solute
dissolved in a
solvent
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.
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
2. Pressure
Increase in temp
Usually has little, if
generally increases
any, effect on solid
solubility of a solid in
and liquid solutes.
a liquid
Increase in pressure
Increase in temp
increases the
decreases solubility
solubility of a gas in
of a gas in a liquid.
a liquid.
Specific concentration
Can
be defined as percent by
volume or percent by mass
Example: 3% hydrogen
peroxide or 25% fruit juice.
MOLARITY
Acids
Very important
chemicals in
everyday life
processes.
Properties of acids:
1.
2.
3.
4.
Sour taste (never taste a chemical)
All contain hydrogen
Also called “proton donors”
React with active metals to produce
hydrogen gas.
Zn +
2HCl
ZnCl2 + H2
Indicators
A.
B.
C.
D.
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)
Common acids
Sulfuric (H2SO4) used in car batteries
Nitric (HNO3) used in 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
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.
These are double replacement
reactions.
What determines if an acid is
classified as “strong” or weak?
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.