Acid and Bases

pH

⦿ Any number below 7 is considered an

acidic solution. It also means there are more
H+ ions than OH- in the solution.

⦿ Any number above 7 is considered an

alkaline (basic) solution. It also means there
are more OH- ions than H+ ions in the
solution.

⦿ Any number equal to 7 is considered

neutral. The number of H+ ions equals the
number of OH- ions in the solution.

pH scale

⦿ The closer a solution’s pH is to 1, the more acidic

the solution (example: a pH of 3 is more acidic
than a pH of 6)

⦿ The closer a solution’s pH is to 14, the more basic

the solution (example: a pH of 13 is more basic
than a pH of 8)

⦿ Hydrochloric acid has a pH of 2. It is produced

by your stomach lining to aid in digestion.

⦿ Lye which is used in common household

cleaners, such as oven cleaner, has a pH of 13.

⦿ Water has a pH of 7and is considered neutral.

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Properties of acids

⦿ Acids have more H+ ions in the solution
⦿ Aqueous solutions of acids have a sour

taste.

⦿ Acids change the color of acid-base

indicators.

⦿ Some acids react with active metals to

release hydrogen gas.

⦿ Acids react with bases to produce salts and

water.

⦿ Acids conduct electric currents

Properties of bases

⦿ Bases have more OH- ions

⦿ Aqueous solutions of bases taste bitter.

⦿ Bases change the color of acid-base

indicators.

⦿ Dilute aqueous solutions of bases feel

slippery.

⦿ Bases react with acids to produce salts and

water.

⦿ Bases conduct electric currents.

Why is pH important?

⦿

pH must be carefully regulated in an organism; if too high or too
low, the organism will die. (The pH of blood in humans is 7.4. Our
body is naturally capable of monitoring and addressing changes
in the pH level.)

⦿

Even if the pH is too low, your body will signal mechanisms to
neutralize the condition using bicarbonate from your pancreas
and liver.

⦿

Fish are dependent on the pH of the water where they live. If the
pH does not remain stable, the fish will die.

⦿

Gardeners and soil scientists use soil pH as a way to determine
the best plants to grow in a particular area. Gardeners may
adjust the pH of the soil in order to grow a greater variety of
vegetables.

Why is pH important?

⦿ Pool owners must keep a careful record of the

pH of the water. Chemicals (acid or alkali) are
added to maintain the balance.

⦿ Aquariums, either at home or in national

facilities, measure pH of the water in order to
maintain a healthy environment for the
organisms.

⦿ Many careers depend on the knowledge of pH

including agriculture, forestry, food science
(chefs, bakers), oceanography, and of course
medicine.