acids and alkalis

1. Acids and Alkalis
Chapter 10
Chemistry
3rd week

2. Neutralisation
- When an acid reacts with an alkali
Neutralisation process occurs

3. - Neutralisation reaction equation:
Acid + alkali salt + water
Some examples of neutralisation processes:
Hydrochloric
acid
Sodium
Hydroxide
Water
Sodium
Chloride
+ +
Sulphuric
acid
+
Potassium
Hydroxide
Potassium
sulphate
+ Water

4. Nitric acid
Sodium
Hydroxide
Water
Sodium
Nitrate
+ +
- Sodium hydrogen carbonate (sodium bicarbonate) is a white solid.
- It is not an alkali, but, when dissolved in water it produces an
alkaline solution.
Sodium
hydrogen
carbonate
Hydrochloric
acid
Water
Sodium
Chloride
+ ++
Carbon
dioxide

5. Using Neutralisation reactions
- Insect stings
- Bee sting (acidic)
- Wasp sting (alkaline)
Neutralised by Soap (alkali)
Neutralised by
Vinegar (weak acid)
Bee Wasp

6. - Curing indigestion
- Indigestion is caused by the stomach making too much
acid to digest food.
- Indigestion tablets contain sodium bicarbonate which
dissolves to form an alkaline solution.
- This alkaline solution neutralises the stomach acid and
cures indigestion.

7. - Baking a cake
- Baking powder contains a mixture of an acid and sodium
bicarbonate.
- When baking powder is mixed with water and flour to
make a cake
- The CO₂ forms bubbles in the mixture making it rise and giving it
the light texture.
Sodium
bicarbonate
solution
acid Water+ +Carbon
dioxide

8. - A model volcano
- You used to make a model volcano using vinegar
and baking soda.
- This is actually a neutralisation reaction.

9. - Fighting a fire
- The soda-acid fire extinguisher contains a
bottle of sulphuric acid and a solution of
sodium bicarbonate.
- When the plunger is struck or the extinguisher
turned upside down, the acid and alkali react
forming CO₂.
- The pressure of the CO₂ produced pushes the water
out of the extinguisher.

10. - Improving crop growth
- Acidity in the soil affects crops
and make the produce less food.
- Lime (calcium hydroxide) is used
to neutralise acidity in soil.
Fields appearing white
after application of lime

11. Acid rain
- Natural acid rain
- CO₂ in the air dissolves in the water in
clouds forming Carbonic acid (weak acid)
- When this weak acid falls on
limestone a reaction occurs and some
of the limestone is washed away.
Cracks called grikes appear

12. - In most of the places where most of the
limestone surface is dissolved away,
pinnacles of rock appear.

13. - The acid rain sinks into the rock and
forms underground streams.
- The water passing in the underground streams
dissolves more rock and forming caves.

14. - As the caves grow
bigger the walls
become weaker and
collapse forming a
gorge.

15. Air pollution and acid rain
- Fuels such as coals and oil contain sulphur.
- When the fuel is burnt it reacts with the
oxygen in the air to form sulphur dioxide.
- The sulphur dioxide reacts with the oxygen and
water in the air to form sulphuric acid.
- Factories and cars also produce nitrogen oxides
which produces nitric acid.

16. The effect of acid rain
- When acid rain
reaches the ground it
dissolves some of the
minerals in the soil
and carries them
away. This is called
leaching.

17. - Some of these minerals
are needed for healthy
growth of the plants