Page 29 - Ranger SPM 2022 Chemistry

Chemistry SPM Chapter 2 Carbon Compound
(c) Dehydration of alcohol with acidified potassium
• Alcohol undergoes dichromate(VI) solution.
dehydration by passing • C H OH(l) + 2[O] →
5
2
alcohol vapour over a heated CH COOH(l) + H O(l)
3
2
catalyst (porcelain chips,
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aluminium oxide, alumina or
concentrated sulphuric acid)
to produce alkene gas. Water out
• The heated catalyst is used
to remove water molecules
from ethanol. Water Liebig condenser
• C H OH(g) → in
2
5
C H (g) + H O(g)
2
2
4
Ethanol, C H OH +
5
2
H H H H oxidising agent
& &
H!C!C!H C"C + H O
2
& & H H Water
H OH
Porcelain chips Heat
Glass wool
soaked in Diagram 2.11
ethanol,
C H OH
2 5 Gas
Heat 2. Carboxylic acid undergoes four
chemical reactions:
Water
(a) Carboxylic acid + base →
carboxylate salt + water
Diagram 2.10
• The gas released and 1.0 mol dm –3
collected in the test tube aqueous
is tested with the following hydroxide
solution
reagents to show that the
gas is alkene gas.
Diluted
Reagent used Observation ethanoic
acid
Bromine water The brown colour of
Form 5
bromine water turns Diagram 2.12
colourless.
Acidified The purple colour of Type of Observation
potassium acidified potassium base
manganate(VII) manganate(VII) Copper(II) • Black powder dissolves
solution solution turns oxide in ethanoic acid forming
colourless. a blue solution.
• Blue solid is formed.
Carboxylic acid Sodium • Colourless solution is
formed.
1. Carboxylic acid can be prepared in hydroxide • White solid is formed.
solution
the laboratory through oxidation

158

02.5 RANGER SPM CHEMISTRY 2P.indd 158 29/03/2022 2:28 PM