chem f4

1. ACIDS AND BASES
KNOWING ACIDS…

2. MEANING OF ACID
• According to Arrhenius,
An acid is a chemical compound that
produces hydrogen ions, H+ or
hydroxonium ions H3O+ when it
dissolves in water.

3. Knowing acids..
• Acids can be divided into
– Monoprotic acid
HNO3(aq) H+ + NO3-
– Diprotic acid
H2SO4(aq) 2H+ + SO42-

4. Knowing acids…
• It is also divided into mineral acid and
organic acid.
Type of
acid
Example
Mineral
acid
Hydrochloric acid, HCl, sulphuric acid
H2SO4 and nitric acid HNO3.
Organic
acid
Ethanoic acid CH3COOH, methanoic
acid HCOOH, ethanedioic acid
H2C2O4.

5. Role of water
• An acid only shows its acidic
properties when water is present.
• In water, acid will ionise to form H+,
that are responsible for acidic
properties.
• (Experiment 7.1)

6. Chemical properties of
acids
• Acids are sour in taste
• Acids have pH values of less than 7.
• Acid changes the colour of these
indicators:
Indicator Colour of indicator
Blue litmus paper Red
Universal indicator Orangeandred
Methyl orange Red

7. Chemical properties of acid
• Acid can react with bases to produce
salts and water
H2SO4 + CuO CuSO4 + H2O
• React with metals to produce salts and
hydrogen
H2SO4 + Mg H2 + MgSO4

8. Properties of acid
• React with carbonates to produce salts,
carbon dioxide and water
2HCl + CuCO3 CuCl2 + CO2 + H2O
• Aquoeus solution of acids can conduct
electricity because the acid molecules
can ionise to produce free mobile ions

9. The strength of acids
• Acids can be divided into
1. Strong acid – an acid which ionises
completely in water to produce higher
concentration of hydrogen ions
HNO3 H+ + NO3
-
2. Weak acid – an acid which ionises
partially in water to produce a lower
concentration of hydrogen ions.
CH3COOH CH3COO- + H+