1. Acids and Alkalis
Grade 10

2. Acids Sour Turn litmus red pH less than 7 Dissolve carbonate rocks
Corrode metals
Conduct electricity

3. Acids
Acids are substances that give H+ ions when added to water.

4. Alkalis
Bitter
Turn litmus blue
pH greater than 7
Slippery
caustic

5. Alkalis
An alkali is a substance that gives OH- ions when added to water

6. Neutralizations reactions
Acids and alkalis neutralize each other to form a salt
Example: HCl + NaOH  NaCl + H2O
Reactions of acids and alkalis are called neutralization reactions

7. Neutralization examples
Indigestion is caused by too much amounts of hydrochloric acid in the stomach.
It is cured by indigestion tablets.
Indigestion tablets contain magnesium oxide that neutralises the excess HCl.

8. Neutralization examples
Fields with acidic soil can be improved by adding lime.
The lime contains calcium hydroxide Ca(OH)2 which is an alkali

9. Neutralization examples
Lakes affected by acid rain can be neutralized by adding lime.

10. Strong vs. weak Strong = complete dissociation
Example, when HCl is dissolved in water, all of it becomes H+ + Cl HCl, H2SO4, HNO3
HCl  H+ + Cl-
H2SO4  2H+ + SO4 2-
Weak = incomplete dissociation
Acetic acid (vinegar) is a weak acid
CH3COOH, small amounts dissociate into H+ and CH3COO CH3-COOH, H2CO3, HF
CH3COOH CH3COO H+
More dissociation = stronger acid

11. Strong bases dissociate completely
NaOH, KOH, Ca(OH)2
NaOH  Na OH-
Weak bases dissociate partially
Mg(OH)2, Fe2O3, NH4OH
NH4OH NH OH-
If a base is soluble in water, it is called an alkali.
NaOH, KOH

12. Strong and weak bases Strong bases ionises completely NaOH  Na+ + OH-
NaOH, KOH, Ba(OH)2, Ca(OH)2
Weak bases ionises partially
Mg(OH)2, CuO, Al2O3, NH4OH
Strong acids have a small pH
strong bases have large pH
Neutral solutions have pH 7
Smaller the pH, stronger the acid
Larger the pH, stronger the base

13. Indicators Indicators are substances that change
colour when placed in an acid or an alkali.
There are four important indicators:
Methyl orange
Phenolphthalein
Litmus paper
Universal indicator.

14. Procedure:. put 3 cm3 of HCl in a test tube
Procedure: put 3 cm3 of HCl in a test tube. Add few drops of methyl orange. record your observation.
Methyl orange
Phenolphthalein
Litmus paper
Universal indicator
HCl
Red
Colourless
NaOH
Orange/yellow
Pink
Blue
Purple/violet

15. REACTIONS OF ACIDS Neutralisation
Acid reacts with a base to form salt and water.
Base can be a metal oxide or metal hydroxide.
Ammonium hydroxide is also a base.
Calcium oxide + Nitric acid  Calcium nitrate + water
CaO + HNO3  Ca(NO3)2 + H2O
Copper(II) oxide + Hydrochloric acid  Copper(II)chloride + water
CuO + HCl  CuCl2 + H2O
Sodium hydroxide + Sulphuric acid  Sodium sulphate + water
2NaOH + H2SO4  Na2SO4 + 2H2O
Ammonium hydroxide + hydrochloric acid 
Ammonium chloride + water
NH4OH + HCl  NH4Cl + H2O

16. Acid reacts with metals to form salt and hydrogen gas
Most metals react with dilute acids to form salt and hydrogen
Copper, Silver, Gold etc do not react with acids easily because
these metals are not reactive.
Magnesium + sulfuric acid  Magnesium sulfate + Hydrogen
Mg + H2SO4  MgSO4 + H2
Zinc + Hydrochloric acid  Zinc chloride + Hydrogen
Zn + HCl  ZnCl2 + H2
Acids react with carbonate to form salt, carbon dioxide and water
Sodium carbonate + Hydrochloric acid 
Sodium chloride + Carbon dioxide + water
Na2CO HCl  NaCl + CO2 + H2O
Copper(II) carbonate + sulphuric acid 
Copper(II) sulphate + Carbon dioxide + water
CuCO3 + H2SO4  CuSO4 + CO2 + H2O

17. Salts Salts formed from an acid and a base.
First part of a salt is from the base (+)
Second part from the acid (-)
For example, Sodium chloride is a salt.
Sodium part comes from a base like sodium hydroxide.
Chloride part comes from an acid (hydrochloric acid)
Second part of the salt depends on the acid.
Hydrochloric acid HCl chloride Cl (-)
Sulphuric acid H2SO4 - sulphate SO4 (2-)
Nitric acid HNO nitrate NO3 (-)
Carbonic acid H2CO carbonate CO3 (2-)
Phosphoric acd H3PO phosphate PO4 (3-)

18. How to make salts? Acid react with metal
Example: Making Zinc sulphate.
Take sulphuric acid in a beaker.
Add excess zinc and warm the mixture.
Wait until no more bubbles come out.
Cool the mixture and filter to get rid of excess Zinc.
Take the filtrate in an evaporating dish, heat and
evaporate until crystallisation point.
Cool it in room temperature to get the crystals of Zinc
sulphate.

20. Two soluble chemicals
Best example is acid and alkali reaction(neutralisation) and a salt is made.
Example: When hydrochloric acid and potassium hydroxide
solution are mixed, we can make Potassium chloride salt.
KOH (aq) + HCl (aq)  KCl (aq) + H2O (l)
First conduct a titration to know what volume of acid and base
exactly required for neutralisation.
Then mix acid and base in larger volume in the same ratio you
found in the titration for complete neutralisation.
Heat and evaporate the resulting solution until crystallisation.
Cool it to get the crystals of potassium chloride.

22. Double decomposition or Precipitation.
This method is useful to make a salt which is insoluble in water.
For example to make calcium carbonate salt which is
insoluble. Mix solutions of sodium carbonate and calcium chloride; both soluble and the calcium carbonate precipitates.
Na2CO3 (aq) + CaCl2 (aq)  CaCO3 (s) + 2NaCl (aq)
When two soluble salt solutions when mixed, the insoluble salt is precipitated out.
The mixture is then filtered and the solid salt is left for
drying.

24. Soluble and insoluble
Following statements help you to identify if a chemical can dissolve in water or not.
All compounds of SODIUM, POTASSIUM and AMMONIUM are
soluble in water.
All NITRATE compounds are soluble.
All CHLORIDES are soluble except Silver chloride and
Lead(II) chloride.
All SULPHATES are soluble except Barium sulphate and
Lead(II) sulphate.
All CARBONATES are insoluble except sodium carbonate,
potassium carbonate and ammonium carbonate.
All metal oxides and metal hydroxides are insoluble in water except sodium, potassium and calcium oxide/hydroxide.

25. Soluble or insoluble??? Sodium carbonate Na2CO3 Soluble
Copper(II) sulphate CuSO4
Lead(II) chloride PbCl2
Insoluble
Silver sulphate Ag2SO4
Barium chloride BaCl2
Ammonium sulphate (NH4)2SO4
Iron(III) oxide Fe2O3

26. Copper(II) hydroxide Cu(OH)2
Insoluble
Silver chloride AgCl
Barium sulphate BaSO4
Lead(II) nitrate Pb(NO3)2
Soluble
Sulphuric acid H2SO4
Potassium chloride KCl
Calcium sulphate CaSO4
Magnesium carbonate MgCO3

27. THE END