Chapter 7 | Acids, Bases And Salts • pH • Ionic Reactions [1]

Question 1

ACIDS

What are acids?

Answer 1

ACIDS are substances which produce hydrogen ions (or protons) [H+] or hydroxonium ions [H30+] as the only positive ions when dissolved in water.

Question 2

Ionisation

Answer 2

Acids dissolve in water to produce hydrogen ions, H+, as the only positive ions, together with the corresponding negative ions. This process is known as ionisation.
Therefore, ionisation can be said to be the dissolution of ions in water.

Question 3

Examples of Acids

Answer 3

Common examples of acids include:
- Hydrochloric acid
⊹₊ ⋆＊ [HCl]
HCl »»»» H+ † Cl–

• Tetraoxo-sulphate (VI) acid
  ⊹₊ ⋆＊ [H2SO4]
• Trioxonitrate (V) acid
  ⊹₊ ⋆＊ [HNO3]
• Trioxocarbonate (IV) acid
  ⊹₊ ⋆＊ [H2CO3]
• Tetraoxophosphate (V) acid
  ⊹₊ ⋆＊ [H3PO4]
• Trioxosulphate (IV) acid
  ⊹₊ ⋆＊ [H2SO3]

Note: Numbers are subscripts.

Question 4

Equations that proof the above definition of acids.

Answer 4

HCl(g) + H2O —» H3O+(aq) + Cl-
HNO3 + H2O —» H3O+(aq) + NO3-
H2SO4(aq) + H20 —» 2H3O+(aq) + SO²-4

And so on…

Question 5

The presence of hydrogen in acids

Answer 5

The characteristic properties of an acid in solution are you to the presence of these hydrogen ions.
This is seen when dry hydrogen chloride gas is dissolved in water and in methyl benzene.
- In water, it forms hydrogen ions and behaves like a typical acid.
- In methyl benzene, it does not form hydrogen ions and does not show any acidic properties.

Thus, an acid has at least one ionisable hydrogen atom in its molecule.

Question 6

Classes of Acids

Answer 6

There are two classes of acids
- organic acids and
- mineral or inorganic acids.

The former occur as natural products in plant or animal materials;
while
The latter can be prepared from mineral elements or inorganic matter.

Question 7

Organic Acids

Answer 7

As the name suggests, organic acids are acids that are got from plant and animal sources. They occur as natural products in plants and animals.

Some examples of organic acids are:

• Ethanoic acid
  ⊹₊ ⋆ Source » Vinegar
• Lactic acid
  ⊹₊ ⋆ Source » Milk
• Citric acid
  ⊹₊ ⋆ Source » Lime, Lemon
• Amino acids
  ⊹₊ ⋆ Source » Proteins
• Fatty acids
  ⊹₊ ⋆ Source » Fats and Oils
• Ascorbic acid [vitamin c]
  ⊹₊ ⋆ Source » Oranges

Question 8

Inorganic Acids

Answer 8

Also, as the name suggests, inorganic acids are acids got from inorganic sources or mineral sources These sources could be anything from petroleum or diesel to nnn

Examples of inorganic acids are:

• Hy