Page 42 - Spotlight A+ Form 4 & 5 Chemistry KSSM

Form
5 Chemistry Chapter 1 Redox Equilibrium

CHAP. (v) Write the ionic equation to represent the reaction that take place in test tube P. C3 [1 mark] CHAP.
1 (b) 1,1,1-trichloromethane is added to test tubes P and Q. The mixture in both test tubes are shaken gently. 1

(i) Predict the colour of 1,1,1-trichloromethane in both test tubes. C4 [1 mark]
(ii) Explain the formation of the colour of 1,1,1-trichloromethane in test tube Q. C3 [1 mark]

Section B

SPM CLONE
2. Figure 2.1 shows the electrolysis of potassium chloride, KCl solution using carbon electrodes.
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Hydrogen Chlorine gas
gas, H
2 1.0 mol dm –3
potassium chloride,
KCl solution
Carbon
electrode P Carbon
electrode Q

Figure 2.1
(a) State the factors that determine the products formed at electrode P and electrode Q. C2 [2 marks]
Given that:
Cl + 2e  2Cl – E = +1.36 V
–
0
2
O + 4H + 4e  2H O E = +1.23 V
+
–
0
2
2
2H O + 2e  H + 2OH – E = –0.83 V
–
0
2
2
K + e  K E = –2.93 V
–
0
+
(b) Explain the reactions at electrodes P and Q. Include the following in your explanation: C4
(i) List of cation and anion of electrolyte attracted to each of electrodes, P and Q. [2 marks]
(ii) Names of the chemical species oxidised and reduced at each electrode. [2 marks]
(iii) The reason why the chemical species are chosen to be oxidised or reduced. [4 marks]
(iv) Half equations for each reaction. [2 marks]
SPM CLONE 0
(c) Figure 2.2 shows a voltaic cell. Given that E value
of Q is more positive compared to copper, Cu. V
(i) State the positive and negative terminal of
the cell. C2 Metal Q Copper,
(ii) Suggest metal Q and suitable solution to be Cu metal
solution R. C3 Solution R Copper(II) nitrate,
Cu(NO ) solution
[4 marks] 3 2
Figure 2.2
Section C
SPM CLONE
3. (a) Two different metals are placed in a lime. The circuit is
completed by connecting the metals to a voltmeter as shown Voltmeter
in Figure 3.1. What happens to the iron nail? Write a half
equation for the reaction. C3 [2 marks]
Copper,
Iron, Cu coin
Fe nail Lime
Figure 3.1
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