1. Acids, Bases and Salts
Mrs Teocc

2. Acids Acids Strong acids Weak acids man-made mineral acids corrosive
e.g. sulphuric acid hydrochloric acid nitric acid
Weak acids
found in plants and animals, used in food
organic acid
not very corrosive
e.g. ethanoic acid citric acid malic acid

3. Physical Properties of Acids
1. Acids have a taste.
sour
Lemons, limes, oranges, grapefruits - citric acid
Grapes – tartaric acid

4. Physical Properties of Acids
2. Acids can the colour of indicators
change
Indicator
Colour in acid
Blue Litmus
Phenolphthalein
Methyl orange
Red
Colourless
Red

5. Chemical Properties of Acids
An acid reacts with a metal to form
a salt and hydrogen
acid + metal  salt + hydrogen
e.g 1. zinc + hydrochloric  acid
2. Magnesium + sulphuric  acid
zinc + hydrogen chloride
Zn HCl  ZnCl H2
zinc + hydrogen sulphate
Mg + H2SO MgSO H2

6. Chemical Properties of Acids
acid + metal  salt + hydrogen

7. Chemical Properties of Acids
acid + metal  salt + hydrogen
Note:
1. Different metals have different rates of reaction with dilute acids.
2. Sodium , potassium, lithium react explosively with dilute acids.
3. Copper, silver, gold do not react with dilute acids.

8. Chemical Properties of Acids
a salt + water
2. An acid reacts with a base to form
acid base  salt + water
e.g.
(a) copper(II) + sulphuric  oxide acid
(b) sodium hydrochloric  hydroxide acid
copper(II) + water sulphate
CuO H2SO4  CuSO H2O
sodium + water chloride
HCl NaOH  NaCl H2O

9. Chemical Properties of Acids
The reaction between a base and an acid to produce a salt and water is called
neutralisation.

10. Chemical Properties of Acids
3. An acid reacts with a carbonate to produce
a salt, water and carbon dioxide
acid + carbonate  salt + water + carbon dioxide eg. (a)magnesium +hydrochloric  carbonate acid
magnesium + water + carbon chloride dioxide
MgCO HCl  MgCl H2O CO2

11. Chemical Properties of Acids
carbonate + acid  salt + water + carbon dioxide
White precipitate is formed

12. Properties of Acids Summary 1. Acids have a sour taste.
2. Acids change the colour of indicators
3. acid + metal 
4. acid + base 
5. acid + carbonate 
salt + hydrogen
salt + water
salt + water +carbon dioxide

13. Explanation for Properties
1. When an acid dissolves in water,
it undergoes ionisation.
H+ ions and the corresponding acid polyatomic ions are formed.
The properties of an acid are due to the presence of hydrogen ions.

14. Hydrogen ions and Acids
citric acid water (hydrogen citrate)
sulphuric acid water (hydrogen sulphate)
hydrochloric acid + water (hydrogen chloride)
H+ ion + citrate ion
H+ ion + sulphate ion
H+ ion + chloride ion
When acid dissolves in water, H+ ions are formed

15. Hydrogen ions and Acids
An acid is a substance that produces hydrogen ions in water

16. Strength of Acids Acids Strong acids Weak acids
all the acid molecules ionise to become ions
Weak acids
most molecules remained unchanged

17. Some Uses of Acids Hydrochloric acid Sulphuric acid Nitric acid
Cleaning metallic surfaces before they are painted or coated with other metals
Used as an in car batteries, making fertilisers, and plastics Making fertilisers and explosives
Preserving food and cooking
Making health salts
Hydrochloric acid
Sulphuric acid
Nitric acid
Ethanoic acid
Citric acid

18. Bases and Alkalis Bases
* aqueous ammonia * metal oxides and metal hydroxides e.g. copper (II) oxide, zinc oxide, magnesium oxide, sodium oxide, zinc hydroxide, potassium hydroxide
Alkalis
* aqueous ammonia
* metal hydroxides which are soluble in water e.g. calcium hydroxide, sodium hydroxide, potassium hydroxide

19. Bases and Alkalis BASES ALKALIS e.g. NaOH
e.g.CuO
ALKALIS
e.g. NaOH
Alkalis are bases but not all bases are alkalis

20. Physical of Properties of Alkalis
Alkalis feel
Alkalis taste
soapy.
bitter.

21. Physical of Properties of Alkalis
3. Alkalis change the colour of indicators
Indicator
Colour in Alkali
Red litmus
Blue
Phenolphthalein
Pink
Methyl Orange
Yellow

22. Chemical Properties of Alkalis
1. An alkali reacts with an acid to produce
a salt and water only.
acid + alkali  salt + water e.g. (a) copper(II) + sulphuric  oxide acid
(b) sodium + hydrochloric  hydroxide acid
copper(II) +water sulphate
CuO H2SO4  CuSO H2O
sodium + water chloride
HCl NaOH  NaCl H2O

23. The reaction between an alkali (base) and an acid to produce a salt and water is called
neutralisation.

24. Chemical Properties of Alkalis
2. An alkali reacts with an ammonium aalt to produce
a salt, water and ammonia gas.
alkali + ammonium salt  salt + water + ammonia gas e.g. ammonium chloride + sodium hydroxide 
sodium chloride + water + ammonia
NH4Cl + NaOH  NaCl + H2O + NH3

25. Chemical Properties of Alkalis
3. An alkali reacts with a solution of metal salt to form a metal hydroxide.
e.g. FeCl NaOH  Fe(OH) NaCl (red-brown ppt)
CuSO NaOH Cu(OH) Na2SO (blue ppt)

26. salt + water + ammonia gas.
Properties of Alkalis
Summary
1. Alkalis feel soapy.
2. Alkalis change the colour of indicators
3. alkali + acid 
4. alkali + ammonium salt 
5. alkali + solution of metal salt 
salt + water.
salt + water + ammonia gas.
metal hydroxide + salt

27. Hydroxide ions and Alkalis
When an alkali dissolves in water hydroxide ions (OH-) ions are produced.
e.g NaOH  Na OH KOH  K OH-
* Properties of alkalis are due to the presence of hydroxide ions.

28. Strength of Alkalis Alkalis Strong alkalis Weak alkalis
when the alkali is dissolved in water, all the ions are dissociated
Weak alkalis
most molecules remained unchanged

29. Strength of Alkalis Strong alkalis e.g. NaOH  Na+ + OH-
KOH  K OH-

30. Strength of Alkalis Strong alkalis e.g. NaOH  Na+ + OH-
KOH  K OH-
OH-
Na+
OH-
Na+
Na+
OH-
OH-
Na+

31. Strength of Alkalis Weak alkalis e.g. NH3 + H2O NH4+ + OH-
- Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchanged

32. Strength of Alkalis Weak alkalis e.g. NH3 + H2O NH4+ + OH-
- Only a small fraction of ammonia molecules form OH- - Most of molecules remained unchanged
NH3
NH3

33. Uses of bases/alkalis mainly for 2 reasons neutralise acids
e.g. toothpaste (magnesium hydroxide)
antacid (aluminium hydroxide, magnesium hydroxide)
remove grease
e.g. soap, floor cleaners (strong alkali-sodium hydroxide)
cleaners for glass windows (weak alkali/ /ammonia)

34. Uses of Alkalis Alkalis Common names Uses
Sodium hydroxide caustic soda Making soap, washing powder, drain cleaner
Potassium hydroxide caustic potash Making paint removers dyes for fabric Calcium hydroxide slaked lime Reducing acidity of soil and making mortar
Aqueous ammonia Making fertilisers and (Ammonia solution) household cleaning liquids