This document discusses acids and alkalis. It defines acids as substances that produce hydrogen ions in water, and provides examples like hydrochloric acid. Acids have properties like a sour taste, turning litmus red, and reacting with metals and carbonates. Alkalis are defined as metal oxides or hydroxides soluble in water, with examples like sodium hydroxide. Alkalis have properties like a bitter taste, turning litmus blue, and reacting with acids. The document also describes how acids and alkalis neutralize each other to form salts and water.

1. Chapter Three

2.  An acid is a substance that produces hydrogen
ions when dissolved in water.
 Examples of acids are hydrochloric acid (HCl),
sulphuric acid (H2SO4), nitric acid (HNO3) and
ethanoic acid (CH3COOH).
 Sulphuric acid is used in detergents, fertilisers and
car batteries.
 Ethanoic acid is used in vinegar and making
adhesives.
 Hydrochloric acid is used in leather processing and
cleaning materials.

3.  Acids have a sour taste.
 Acids dissolve in water to form solutions that
conducts electricity.
 Acids turn blue litmus red.
 Acids have pH value less than 7.
 Acids react with metals, carbonates and bases.

4. Metal reactions
 Acid + Reactive Metal Salt + Hydrogen
Carbonate reactions
 Acid + Carbonate Salt + Water + Carbon dioxide
Base reactions
 Acid + Base Salt + Water

5.  Test for Hydrogen
 Place a lighted splint at the mouth of a test tube.
 A pop sound is heard and the splint is extinguished.
Hydrogen is thus present.
 Test for Carbon dioxide
 Bubble the gas through limewater.
 If carbon dioxide is present, the limewater will turn
chalky and a white precipitate would be formed.

6.  An alkali is a metal oxide or hydroxide that is
soluble in water.
 Examples :
 sodium hydroxide (NaOH)
 potassium hydroxide (KOH)
 calcium hydroxide [Ca(OH)2]
 barium hydroxide [Ba(OH)2]
 aqueous ammonia (NH3).

7.  Ammonia solution
 Fertilisers
 Window cleaning solutions
 Calcium oxide
 To neutralise acidic soil
 Iron, concrete and cement
 Magnesium hydroxide
 Toothpaste to neutralise acid on teeth
 Antacids to relieve indigestion
 Sodium hydroxide
 Soaps and detergents
 Industrial-cleaning detergents

8.  Alkalis have a bitter taste and soapy feel.
 Alkalis dissolve in water to produce hydroxide
ions.
 Alkalis turn red litmus blue.
 Alkalis have pH value more than 7.
 Alkalis react with metals, ammonium salts and
acids

9. Metal reactions
 Alkali + Salt A Metal hydroxide + Salt B
Ammonium salt reactions
 Alkali + Ammonium Ammonia + Water + Salt
Base reactions
 Alkali + Acid Salt + Water

10. Taste Solubility
 Acids have a sour taste.
 Acids dissolve in water
to form solutions that
conducts electricity.
 Acids turn blue litmus
red.
 Acids have pH value less
than 7.
 Acids react with metals,
carbonates and bases.
 Alkalis have a bitter
taste and soapy feel.
 Alkalis dissolve in water
to produce hydroxide
ions.
 Alkalis turn red litmus
blue.
 Alkalis have pH value
more than 7.
 Alkalis react with
metals, ammonium salts
and acids.
Litmus pH value Reactions

11. Test for Ammonia
 Place a piece of moist red litmus paper in the
solution
 If ammonia is present, the moist red litmus paper
will turn blue.

12. Indicator Colour in Acids pH value Colour in Alkalis
Methyl orange Red 3 – 5 Yellow
Screened Methyl orange Violet 3 – 5 Green
Litmus paper Red 5 – 8 Blue
Bromothymol blue Yellow 6 – 8 Blue
Phenolphtalein Colourless 8 – 10 Pink
Red cabbage juice Pink Nil Green
Hydrangea flower Blue Nil Red

13.  When an acid and alkali react together, they
neutralise each other. Their properties are
removed.
 The pH value of the acid is increased while the pH
value of the alkali is decreased. The neutral
mixture has a pH value of 7.
 Water is formed together with a new substance
called a salt.

14.  A salt is a ionic compound formed when a metallic
or ammonium ion neutralises hydrogen ions of an
acid.
 Calcium chloride
 CaO + 2 HCl CaCl2 + H2O
 Zinc sulphate
 ZnO + H2SO4 ZnSO4 + H2O
 Sodium nitrate
 NaOH + HNO3 NaNO3 + H2O