Page 8 - 1202 Question Bank Chemistry Form 5 KSSM

• A protective surface prevents water and
Rust (Fe O .xH O)
Drop of water 2 3 2 air from coming into contact with the iron.
Example: paint, grease, oil, plastic, metals
and using other metals.
OH − • Example of using other metals: Galvanisation
O O 2
2 involves coating iron with a layer of zinc. Tin
Fe 2+ plating or tinning is a process of coating iron
e −
with a thin layer of tin. Chrome plating is used
on car bumpers and decorative items.
Anode (–) Cathode (+) (b) Alloying
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2+
Fe(s) Fe (aq) + 2e − O (g) + 2H O(l) + 4e −
2 2 • Alloy such as stainless steel is made of a
−
4OH (aq)
Iron metal mixture of iron with chromium and nickel.
This alloy has a very high resistance to
2. Corroded iron is covered with a layer of red-brown corrosion. Chromium and nickel form oxide
compound. The red-brown compound is hydrated layer that is very strong and impermeable to
iron(III) oxide, Fe O .xH O or rust.
2 3 2 air and water.
3. Corroded copper is covered with a green layer. (c) Sacrificial protection
The green compound is basic copper(II) carbonate, • Involves placing a more electropositive metal
CuCO .
3 in contact with iron.
4. Ways to prevent rusting: • Example: Magnesium acts as a sacrificial
(a) Use a protective surface metal to protect underground iron pipes from
rusting.

PAPER 1

Each question is followed by four options A, B, C or D . Choose the best option for each question.

1.1 Oxidation and Reduction 4. Carbon is a non-metal and it can be used to
SPM reduce metal oxides. In the reactivity series of
SPM
CLONE
metals, carbon is located between
1. Ethanol is the second member of the alcohol
SPM
SPM family. Ethanol reacts with acidified potassium A calcium and aluminium
CLONE B aluminium and zinc
dichromate(VI) to form ethanoic acid. What type C zinc and iron
of reaction is involved in this conversion? D iron and lead
A Esterification C Halogenation
B Dehydration D Oxidation
5. Diagram 1 shows the experimental set-up used
SPM
SPM to investigate a redox reaction. During a redox
2. Oxidising agent is used to oxidise iron(II) sulphate CLONE
SPM
SPM to iron(III) sulphate. Which of the following is reaction, transfer of electron at a distance takes
CLONE place between the oxidising agent and reducing
not an oxidising agent for the reaction? agent which were separated by solution X.
A Chlorine
B Potassium bromide G
C Hydrogen peroxide
D Concentrated nitric acid Graphite electrodes HOTS Analysing
– +
3. What is the oxidation number of hydrogen in
SPM
SPM aluminium hydride, AlH ? Potassium Potassium
CLONE 3 iodide manganate
A −1 C +1 solution (VII) solution
B 0 D +2 Solution X

4 Question 4: Question 5: Diagram 1
SOS TIP Refer to the positions of metals in the reactivity series of metals. Reduction half-equation: 2+ 2
You need to memorise this series.
MnO + 8H + 5e → Mn + 4H O
−
+
−
4
H ions are supplied by aqueous acid solution
+