7.1; Introduction of Acid & Bases : SLISS 2012

2. At the end of this lesson, students are able to:
• State the meaning of acid, base and alkali.
• State uses of acids, bases and alkalis in daily
life.
• Explain the role of water in the formation of
hydrogen ions to show the properties of acids.
• Explain the role of water in the formation of
hydroxide ions to show the properties of alkalis.
• Describe chemical properties of acids and
alkalis.

5. Arrhenius’ definition:
ACID BASE ALKALI
Chemical Chemical Bases that can
dissolve in water to
compound that compound that
produces
ionises to produce can neutralise an
hydroxide ion, OH-
H+ or H3O+ in acid to form salt
water. and water.
H2O H2O
Ex: HCl H+ + Cl- Base + acidsalt + Ex: NaOH (s) Na+
water + OH-
Ex:
MgO, ZnO, NaOH,
KOH

6. The properties of acid is due to the presence
Of hydrogen ions, H+ (aq)
H2O
Acid H+
Without water, acid will not behave as an
acid.

7. The properties of alkali is due to the presence
Of hydroxide ions, OH- .
H2O
Alkali OH-
Without water, alkali will not behave as an
alkali.

8. ACID ALKALI
• Sour taste • Bitter taste
• pH < 7 • pH > 7
• Turn blue litmus • Turn red litmus
paper to red paper to blue
• React with bases to • React with bases to
form salt & water form salt & water

9. Salt & Hydrogen
gas Salt & water
With With
metal ACID base
Ex: H2SO4 + Zn  Ex: HCl + NaOH
ZnSO4 + H2  NaCl + H2O
With metal
carbonates
Salt, carbon dioxide gas & water
Ex: 2HCl + CaCO3  CaCl2 + CO2 +
H2O

10. Metal hydroxide
Salt & water
With With
Ex: Fe3+ + 3OH- metal ALKALI
 Fe(OH)3
acid Ex: HCl + NaOH
ion
(precipitate)
 NaCl + H2O
Heat with
ammonium
salt
Ammonia gas, water and salt
Ex: NH4+ + OH-  NH3 + H2O

11. H2SO4
Uses Of Carbonic Acid
Acid
Benzoic acid, ethanoic acid Nitric Acid, HCl

12. To clean metals before
electroplating.
To make
paints, detergents, fertilizers,
electrolyte.
To coagulate latex.

13. To preserve food
A component of vinegar
To make carbonated acid

14. MgOH: neutralises
acids Uses Of Al(OH)3, Mg(OH)2 : alkali
Alkali neutralise excess acid in
our stomach
NaOH
NH3 solution

15. To make Fertilizers, to keep
latex in liquid form, as a sink
cleaning agent.
To make soap, detergents.
To make toothpaste, gastric
pills (antacids).

16. 7.1 : ASIDS AND BASES
The following is some information on magnesium
hydroxide:
Magnesium hydroxide is one of the ingredients found in
toothpaste and potassium hydroxide is used as the
electroyte in alkaline batteries. Magnesium hydroxide is a
base and potassium hydroxide is an alkaline.
a) What is base?
b) How is alkali different from a base?
c) State three physical properties of an alkali.
d) Write a balanced chemical equation to show the
reaction between hydrochloric acid and
magnesium hydroxide.

17. What is base?
 A base is a substance that react with an acid to form salt
and water only.

How is alkali different from a base?
 An alkali is a soluble base that forms a solution when
dissolved in water and ionises to produce hydroxide ions.

State three physical properties of an alkali.
 Alkali is bitter.
 Slippery.
 Turn red litmus paper blue.

Write a balanced chemical equation to show the reaction
between hydrochloric acid and magnesium hydroxide.
 Mg(OH)2 (s) + 2HCl (aq)  MgCl2 (aq) + 2H2O (l)