Acids and AlkalisChapter 10Chemistry

3rd week

Neutralisation

- When an acid reacts with an alkali

Neutralisation process occurs

- Neutralisation reaction equation:

Acid + alkali salt + water

Some examples of neutralisation processes:

Hydrochloric acid

Sodium Hydroxide WaterSodium

Chloride+ +

Sulphuric acid + Potassium

HydroxidePotassium sulphate + Water

Nitric acid Sodium Hydroxide WaterSodium

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 Chlorid

e+ ++ Carbon

dioxide

Using Neutralisation reactions

- Insect stings- Bee sting (acidic)

- Wasp sting (alkaline)

Neutralised by Soap (alkali)Neutralised by Vinegar (weak

acid)

Bee Wasp

- 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.

- 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

- A model volcano- You used to make a model volcano using

vinegar and baking soda.

- This is actually a neutralisation reaction.

- 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.

- 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

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

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

- The acid rain sinks into the rock and forms underground streams.

- The water passing in the underground streams dissolves more rock and forming caves.

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

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.

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.

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