1. UNIT 1 ACIDS, ALKALIS & CHEMICAL REACTIONS Lesson 4 - Neutralisation

2. Aims of the Lesson
I know that it is possible to mix acids and alkalis together to alter their pH values.
Adding an alkali to an acid increases the pH.
Adding an acid to an alkali decreases the pH.
Water will dilute an acid or alkali when added.

3. Adding Acids and Alkalis Together
Sometimes it is necessary to mix acids and alkalis together.
When this happens the pH of the solutions change.
Can you predict what will happen to an acid with pH value of 1 when an alkali is added to it? Explain.

4. Adding Acids and Alkalis Together
Copy this table in to your jotter and complete as you carry out the experiment:
Volume of Alkali added (cm3)
Colour of Solution
pH of solution 2 4 6 8 10

5. EXPERIMENT Add 10 cm3 of acid to the beaker first.
Then add alkali to the beaker 2 cm3 at a time.
Record the pH using universal indicator and a pH chart (Or pH probe if available).
Complete the table in your jotter.
Take your time, can you get the solution to pH 7?
Repeat the experiment steps 1-5 starting with 10cm3 of alkali

6. Volume of Alkali added (cm3)
Result
Volume of Alkali added (cm3)
Colour of Solution
pH of solution 2
Red 4
Orange 3 6
Orange/Yellow
4/5 8
Yellow 10
Green 7

7. Neutralisation
When an acid (pH 1-6) and alkali (pH 8-14) react together to form neutral solution (pH7)
When this happens two things are always formed
The 2 things always formed are:
A salt … and
Water

8. Neutralisation EXAMPLE OF NEUTRALISATION:
Hydrochloric acid + sodium hydroxide 
Sodium chloride + water
A salt is a product from a chemical reaction between an acid and alkali. The hydrogen atoms in an acid are replaced by the metal atoms of an alkali.

9. Naming Salts How to name a salt:
Hydrochloric acid  ___________ chloride.
Nitric acid  _________ nitrate.
Sulphuric acid  __________ sulphate.

10. PRACTICE EXAMPLE OF NEUTRALISATION: Can you complete the following:
Hydrochloric acid + sodium hydroxide  Sodium chloride water
Can you complete the following:
Nitric Acid + Potassium Hydroxide 
Sulphuric Acid + Lithium Hydroxide 
Nitric Acid + Sodium Hydroxide 
Hydrochloric Acid + Magnesium Hydroxide 

11. Check Test
Discuss in groups the following. What do you think? Who is right?
Neutralisation occurs because they are opposites.
Alkalis neutralise acids
When you add an alkali to an acid the pH will rise beyond 7 and will not stop.
It becomes neutral because we make water during the reaction.
No the pH will stop at 7.