Solutions
Acids and Bases
Solutions
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A solution is a mixture in which one or more
substances are uniformly distributed in another
substance. (Liquids, gases or solids)
The solvent of the solution is the substance in which
the solute is dissolved. (Dissolver)
The solute of the solution is the substance being
dissolved. (Dissolvee)
Every solution has a concentration, or the amount
of solute dissolved in a fixed amount of the solution.
Solutions can become saturated, which means no
more of a solute can be dissolved.
Aqueous solutions are when water is the solvent.
Dissociation of Water
Water molecules are constantly moving.
As they move they bump into each other.
Sometimes this collision is strong enough to
cause a chemical change, where one water loses
a hydrogen.
 H2O ↔ H+ + OH The H+ is known as a proton.
 The OH- is known as a hydroxide ion.
 The free proton joins with a second water and
forms H3O+ which is known as hydronium.
 H+ + H2O ↔ H3O+
 Pure water contains equal amounts of OH - and
H3O+
 This is why water is neutral.
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Acids
Acids have a greater number of hydroniums
(and therefore H+) than hydroxides.
 HCl (Hydrogen Chloride) is a gas. When
dissolved in water: HCl ↔ H+ + Cl The free proton can now join with a water to
make H3O+
 Most acids have a sour taste, but you should
not taste them!!!
 Ex: lemons, vinegar, rainwater, soda,
stomach acid
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Bases
Bases have a greater number of hydroxides
than hydroniums.
 NaOH (sodium hydroxide) is a solid. When
dissolved in water: NaOH ↔ Na+ + OH Alkaline refers to bases.
 Most bases are bitter tasting, but you should
never taste them!!!
 Ex: Baking soda, Antacids, soaps
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pH
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The pH scale measure the amount of H+ in a
solution. It runs from 0 – 14
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It runs on a log scale. Therefore, the difference
between a pH 2 and a pH 3 is 10. We would say
that a pH 2 is 10 times more acidic than a pH 3.
What about a pH 1 and pH 4?
1000 times
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What do the numbers mean?
The pH scale measure the amount of H+ in a
solution.
 pH X tells us that there is a total of 10-X M [H+]
in a solution.
 Ex: pH 5 tells us that there is 10-5 M [H+]
 From pH we can also figure out pOH. pOH
measures the amount of OH- in a solution.
 The sum of pH and pOH should always equal 14.
Ex: pH 5 means pOH 9
 pOH X tells us that there is a total of 10-X M
[OH-] in a solution.
 Ex: pOH 9 tells us that there is 10-9 M [OH-]
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Buffers
This is important because enzymes work in
very narrow pH ranges.
 A buffer is any substance
that neutralize an acid or
a base.
 You have natural buffers in
your body. Ex: the mucus
lining of your stomach buffers the organ
from the high acid that is your stomach acid.
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