Download 7.2 Acids and Bases


Acids and bases are substances that
form ions when dissolved in water.
Acids
Reacts with metals and
carbonates
Conducts electricity
Turns blue litmus paper
red
Tastes sour
pH < 7
Neutralizes bases
Bases
Conducts electricity
Turns red litmus paper
blue
Tastes bitter and feels
slippery
pH > 7
Neutralizes acids

An acid dissolves in water to form
hydrogen ions (H+)
› Example:
HCl (aq)  H+ (aq) + Cl- (aq)

A base dissolves in water to form
hydroxide ions (OH-)
› Example:
NaOH (aq)  Na+ (aq) + OH- (aq)

There are two common groups of
acids:
› Binary Acids
› Oxyacids

Binary acids contain only two elements.
Acid Name
Chemical
Formula
Hydrofluoric acid
HF (aq)
Hydrochloric acid
HCl (aq)
Hydrobromic acid
HBr (aq)
Hydrosulfuric acid
H2S (aq)

Oxyacids are related to polyatomic ions
Acid Name
Chemical
Formula
Nitric acid
HNO3 (aq)
Carbonic acid
H2CO3 (aq)
Sulfuric acid
H2SO4 (aq)
Phosphoric acid
H3PO4 (aq)

Many bases are ionic compounds
containing hydroxide or carbonate ions.
Base
Chemical
Formula
Sodium hydroxide
NaOH (aq)
Calcium hydroxide
Ca(OH)2 (aq)
Magnesium hydroxide
Mg(OH)2 (aq)
Sodium bicarbonate
NaHCO3 (aq)

Acid-base indicators are substances
that changes colour depending on
whether it is in the presence of an acid
or a base.
Acid

Bromothymol Blue (BTB)
› Acid – yellow
› Base - blue
Base
Acid

Phenolphthalein
› Acid – colourless
› Base - pink
Base

Litmus paper
› Acid – red
Base
› Base – blue
Acid

Cabbage juice