Page 20 - 1202 Question Bank Chemistry Form 5 KSSM

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C H AP TE R 1 26. A E value of Zn is more negative than the E value of Fe. Fe is the
CHAPTER 1
cathode and Zn is the anode.
Paper 1 E 0 cell = –0.44 – (–0.76)
= +0.32 V
1. D Acidified potassium dichromate(VI) is an oxidising agent. It 27. A The right-hand side is a chemical cell, S (−) is anode and R (+) is
oxidises alcohols to carboxylic acids. cathode. The left-hand side is an electrolytic cell: P is cathode
2. B Potassium bromide is a reducing agent. Bromide ion is oxidised (−) and Q is anode (+). Reduction occurs at cathodes, R and P.
to bromine. 28. D The right-hand side is a chemical cell: Mg is anode (−); Mg is
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2+
3. A (+3) + 3(x) = 0 oxidised to Mg . The left-hand side is an electrolytic cell: Cu is
2+
3 + 3x = 0 anode (+); Cu is oxidised to Cu .
 x = −1 29. B Cell I: Oxidation of Cu to Cu . Cell II: Oxidation of Cl to Cl .
−
2+
2
4. B Carbon can reduce zinc oxide but cannot reduce aluminium 30. C Anode (P) is plating metal, cathode (Q) is object to be plated
oxide. and electrolyte (R) is silver nitrate.
0
0
5. C KMnO solution acts as an oxidising agent under acidic 31. D E of OH is more negative. OH is oxidised to O gas. E of OH +
–
–
4 2
+
condition. Sulphuric acid supplies the H ions to KMnO . is more positive, H is reduced to H gas.
+
4 2
6. A Combustion of metal in oxygen produces metal oxides are 32. B Higher concentration of Cl , thus Cl ions easier to be oxidised
–
–
redox reactions. at the anode.
7. C A displacement reaction occurred; shows that copper is more 33. B Cells I & III: Hydrogen gas is produced at the cathode and
reactive than metal M. It is more likely to release electrons and chlorine gas is produced at the anode.
be oxidised.
Cell II: Zinc formed at the anode, clorine gas formed at the
8. B Iodide ion is a reducing agent; easily oxidised to iodine. cathode.
9. B Combustion and rusting are redox reactions 34. C Anode: O gas; 4OH → O + 4e + 2H O
−
−
2 2 2
+
−
10. B Cathode: H gas; 2H + 2e → H 2
2
SiO + C ⎯→ Si + CO 2 35. C Hydrogen gas is produced at the cathode and bromine gas is
2
+4 0
+
−
produced at the anode. Na ions combine with OH ions to
11. D Reduction involves loss of oxygen, gain of electrons or gain of
produce sodium hydroxide, NaOH.
hydrogen.
36. B Cell notation of a voltaic cell is written as:
3+
2+
12. B Chlorine water is an oxidising agent that oxidises Fe to Fe . Electrode(s) ǀ Electrolyte(aq) ǁ Electrolyte(aq) ǀ Electrode(s)
Chapter 1
2+
13. C Magnesium displaces Cu ions from copper(II) nitrate. Excess
magnesium powder also observed in the beaker. Electrode Ionic Ionic Electrode
solution solution
14. D 1(+1) + (Cl) + 4(−2) = 0
Cl = +7 Anode (negative terminal) Cathode (positive terminal)
2+
37. B Cu ions are reduced at the cathode to deposit copper metal
15. B A reducing agent releases electrons.
onto the electrode.
2+
2+
16. C Zinc displaces Cu from the solution. When all Cu ions are Cu (aq) + 2e ⎯→ Cu(s)
2+
–
2+
displaced, blue colour disappears and Cu ions change to Cu
38. A Bauxite is an aluminium ore. Aluminium is extracted by
atoms, producing a brown solid.
electrolysis of molten bauxite.
17. A Al and Ca are above Ag in the reactivity series of metals.
39. A Metals above carbon in the reactivity series of metals are
Sulphur is a non-metal.
extracted by electrolysis of their molten ores. Carbon is
−
18. B Chlorine, Cl is an oxidising agent; oxidises I to I . Iodine
2 2 positioned between aluminium and zinc.
solution is brown.
40. C Carbon reduces oxides of zinc and copper. Zinc reduces oxides
19. D Acidified KMnO is an oxidising agent. SO and H S
4 2 2 of iron and copper. Electrolysis is used in purification of metal.
are reducing agents that will react with KMnO , CH is
4 4 41. C Ca is above Mg in the reactivity series of metals.
hydrocarbon.
42. D Iron(III) oxide is reduced by carbon and carbon monoxide to
20. B The chemical formula of chromium(VI) oxide is CrO .
3
iron and carbon dioxide.
21. D A more reactive metal reduces the oxide of a less reactive
43. D Al is formed at the cathode by reduction. Al ions gain
3+
metal. Q > R > S > P
electrons to form Al atoms.
22. B Graphite and platinum are inert electrodes.
44. C Carbon (coke) is more reactive than iron but less reactive
23. D The more positive the E° value, the easier reduction occurs at
than aluminium. Carbon (coke) reduces iron oxide but not
the cathode (positive terminal). aluminium oxide.
E 0 = (+0.34) – (−0.44) = + 0.78 V
cell
45. A Cryolite has a low melting point than bauxite. It reduces the
24. B The more negative the E° value, the more readily for oxidation
high melting point of bauxite thus save energy.
to occur; stronger reduction agent.
46. D A sacrificial metal must be more electropositive than iron.
0
25. D The more positive the E value, the more readily for reduction
A sacrificial metal lose its electrons easier. Sacrificial metal
to occur; stronger oxidation agent.
ionises before iron, corrosion of iron is prevented.
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