1. Acids and Bases
Chapter 32

2. What are Acids?
Acids are common chemicals, some of which are corrosive and dangerous and some of which are quiet harmless.
Strong acids:
Hydrochloric Acid(HCl)
Sulfuric Acid(H2SO4)

3. Some common Acids

4. Bases(or alkalis) Bases are opposite to acids
Bases soluble in water are called alkalis.
Alkalis have a soapy feel.
Examples of bases:
Sodium Hydroxide NaOH
Calcium Hydroxide Ca(OH)2

5. Indicators
An indicator shows by means of a colour change whether a substance is an acid or a base.
Acid turns Litmus from blue to red
Bases turn litmus from red to blue

6. The pH scale
Litmus can only tell if a substance is an acid or base. It cannot tell the different strength of Acids or Bases.
The pH scale indicates the level of acidity or basicity in a solution.
A solution that has a pH of 7 is neutral
A solution that has a pH less than 7 is acidic
A solution that has a pH greater than 7 is alkaline.

7. pH scale

8. Universal Indicator
Universal Indicator can be used to find the exact pH of a substance.
Universal indicator paper changes to a different colour depending on the pH of the solution.

9. Reactions of Acids Acids are involved in the following reactions.
Acid + Base > Salt water
Acid + Carbonate --> Salt + Water + Carbon Dioxide
A salt is formed when the Hydrogen of an
acid is replaced by a metal.

10. Acid + Base
An acid and an alkali neutralise each other in a neutralisation reaction.
Hydrochloric acid and Sodium hydroxide react together to form sodium chloride and water.
HCL + NaOH --> NaCL + H2O

11. To Neutralise an Acid and a Base by Titration
Step 1. Using a pipette,place 20 ml of Sodium Hydroxide into a conical flask and a few drops of litmus indicator.
Step 2. Fill the burette to the top mark with Hydrochloric acid.
Step 3. Adjust level of meniscus of HCl in the burette to zero mark.

12. Step 4. Place the conical flask on a white tile
Step 5. Start adding the acid to the base
Step 6. The acid is added slowly until one drop turns the solution pink. When the indicator has changed colour, stop the titration and note the volume of acid added.

13. Step 7. Repeat the experiment but do not use indicator.
Step 8. The sodium chloride is put in an evaporation dish.
Step 9.The solution is evaporated to dryness and then left to cool
Step 10.A white crystalline substance is formed and sodium chloride has been formed.