pH Scale
What is it? How is it calculated?
What is the pH Scale?


A scale used by chemists to represent how
acidic or basic a solution is. This scale
ranges from 0 to 14.
 A very acidic solution would have a low
pH.
 A very basic solution would have a high
pH.
 A neutral solution such as distilled water
would have a pH of exactly 7.
pH means the power of Hydrogen (the
concentration of hydrogen ions in a
solution).
What is the pH Scale?

The pH is a logarithmic scale. This means that for
every change of one unit on the scale, there would be
a tenfold effect on the concentration of the solution.
A change of 1 pH unit means a 10x change in the concentration (101)
A change of 2 pH units means a 100x change in the concentration (102)
A change of 3 pH units means a ______ change in the concentration (10__)
A change of 6 pH units means a ______ change in the concentration (10__)
pH Scale

The following figure shows the pH
values for various substances.
How is pH calculated?

The formula for determining the pH
value of a solution is:
pH = -log10[H+]



[] – means the concentration of the
hydrogen ions in the solution.
The concentration is in “moles per litre”
(mol/L).
What is the pH of a solution that
contains 0.000 000 36 mol/L of H+
ions?
Some applications of pH

Soil: different kinds of plants grow
best in different pH conditions.
Some applications of pH

Consumer products, such as
shampoo, skin care products,
and cleaning products.
Products with a very high or very low
pH are corrosive and reactive. They
are therefore labeled with HHPS
symbols.
Some applications of pH

Swimming pools: pool water
should maintain a pH range of 7.2-7.8.