Title: Acids%20and%20Bases
1Acids and Bases
2What 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)
3Some common Acids
4Bases(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
5Indicators
- 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
6The 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.
7pH scale
8Universal 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.
9Reactions of Acids
- Acids are involved in the following reactions.
- Acid Base --gt Salt water
- Acid Carbonate --gt Salt Water Carbon
Dioxide - A salt is formed when the Hydrogen of an
- acid is replaced by a metal.
10Acid 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 --gt NaCL H2O
11To 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.
12Step 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.