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pH Scale
2-27-12
Standard: 5d-students know how to use the pH
scale to characterize acid and base solutions
The pH Scale
The pH of a solution is a measure of its
hydronium ion concentration.
The pH scale is a number scale from 0
to 14 to describe the concentration of
hydronium ions in a solution.
A pH of 7 indicates a neutral solution.
Acids have a pH less than 7.
Bases have a pH greater than 7.
If you add an acid to water, the
concentration of H3O+ increases and the
concentration of OH- decreases.
The lower the pH value, the greater
the H3O+ ion concentration in
solution is.
If you add a base to water, the
concentration of OH- increases and the
concentration of H3O+ decreases.
The higher the pH value, the lower
the H3O+ ion concentration is.
Example
Substance A has a pH of 3. Substance B
has a pH of 10.
Is the substance A considered acidic or
basic? Is substance B considered acidic
of basic?
From this does this mean there are
more hydronium ions present or
hydroxide ions present for substance
A? Substance B?
From Friday does this mean your
substances are weak or strong acids or
bases?
Try it on your own
Substance A has a pH of 5,
Substance B has a pH of 9.
Is substance A and B considered
acidic of basic?
From this does this mean there are
more hydronium ions present or
hydroxide ions present for substance
A? Substance B?
Are substance A and B weak or
strong acids or bases?
Exit Question
a) What does the pH scale measure?
Given the following pH numbers is
the sample a base, acid, or neutral?
A) 6
B) 12
C) 7
Please include a reflection on how
you feel about your activity today.