Strength of Acids pH Scale (Power of Hydrogen ion Scale)
Strong Acids Weak Acids The strength of acid or base depends upon
pH value: 0, 1, 2, 3 pH value: 4, 5, 6 the hydrogen ion concentration.
Fully Ionized Partially Ionized pH is a scale which quantifies the
When dissolved in When dissolved in
concentration of hydrogen ion in a
water, they give water, they give
large amounts of H+ small amounts of H+ solution. The range of pH scale is between
ions ions 0 to 14.
HCl (hydrochloric CH3COOH (acetic Substances with a pH value below 7 are
acid), acid), acidic.
H2SO4 (sulfuric HF (hydrofluoric Substances with pH value above 7 are
acid), etc. acid), etc. basic.
Substances with a pH value is 7 are
It is bitter in taste and feels soapy on Substance pH
touch. e.g baking soda Acids
Hydrochloric Acid (HCl) 0
It turns red litmus paper blue.
Sulfuric acid or Battery acid 1.0
Bases are substances made of hydroxide Lemon Juice 2.0
OH- ions and a metal. Vinegar 2.2
Common base are : Sodium hydroxide Apples 3.0
(caustic soda), calcium hydroxide, sodium Wine and Beer 4.0
carbonate (washing soda), lime (Calcium Tomatoes 4.5
oxide), potassium hydroxide (caustic Milk 6.6
Pure Water 7.0
Properties of Base Bases
Human Blood 7.4
1. When used in aqueous state they are good Baking Soda (Sodium 8.3
conductors of electricity. Bicarbonate)
2. Its pH value greater than 7. Ammonia 11.0
3. Strong bases are corrosive
Types of Base
Acid - Base indicators (also known as pH
Base can be divided in two types Water
indicators) are substances which change colour
soluble and water insoluble.
with pH. They are usually weak acids or bases,
Strength of Bases which when dissolved in water dissociate
slightly and form ions.
Strong Bases Weak Bases
pH value: 11, 12, pH value: 8, 9, 10 This range is termed the color change interval.
13, 14 It is expressed as a pH range.
Completely Partially ionize and
ionized in water equilibrium lies
to produce mostly towards
hydroxide ions reactants side
e.g. sodium e.g. ammonia in