Page 27 - Spotlight A+ Form 4 & 5 Chemistry KSSM

Form
5 Chemistry Chapter 1 Redox Equilibrium

CHAP. CHAP.
1 Activity 1.2 1

Aim:
To investigate the conversion of iron(II) ion, Fe to 4. The mixture is filtered into a test tube.
2+
3+
iron(III) ion, Fe and vice versa.
Materials:
–3
0.5 mol dm freshly prepared iron(II) sulphate, Test to confirm the presence of iron(II) ion, Fe .
2+
–3
FeSO solution, 0.5 mol dm iron(III) chloride,
4
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FeCl solution, bromine water, Br , zinc, Zn powder,
3 2
filter paper, 2.0 mol dm sodium hydroxide, NaOH 5. 0.2 mol dm of sodium hydroxide, NaOH
–3
–3
solution solution is added drop by drop until in excess.
The changes are recorded.
Apparatus:
Dropper, spatula, test tube holder, Bunsen burner, Observation:
filter funnel, test tube rack, measuring cylinder, Table 1.2
test tube
Activity Observation
Procedure: Iron(II) sulphate, The brown bromine water,
2+
A Conversion of iron(II) ion, Fe to iron(III) FeSO + bromine Br turns colourless.
ion, Fe 3+ 4 2
water, Br The pale green iron(II)
2
sulphate, FeSO solution
4
turns yellow.
Bromine Adding of sodium A brown precipitate is
water, Br
2
hydroxide, NaOH formed. It is insoluble in
solution excess sodium hydroxide,
Iron(II) sulphate, NaOH solution.
FeSO solution
4
Figure 1.8 Iron(III) chloride, The brown iron(III) chloride,
FeCl + zinc, Zn FeCl solution turns pale
3
3
1. 2 cm of freshly prepared iron(II) sulphate, powder green.
3
FeSO solution is measured and pour into a
4
test tube. Adding of sodium A dirty green precipitate
2. By using a dropper, bromine water, Br is hydroxide, NaOH is formed. It is insoluble in
2
added to the solution in the test tube drop by solution excess sodium hydroxide,
drop until no further changes are observed. NaOH solution.
3. The mixture is shaken well and warm gently.
Inference:
1. The pale green iron(II) sulphate, FeSO solution
4
2+
turns yellow because the iron(II) ions, Fe are
Test to confirm the presence of iron(III) ion, Fe . oxidised to iron(III) ions, Fe .
3+
3+
2. A brown precipitate is formed when tested
with sodium hydroxide, NaOH solution. This
–3
4. 0.2 mol dm of sodium hydroxide, NaOH confirms the presence of the iron(III) ions, Fe .
3+
solution is added drop by drop until in excess. 3. The brown iron(III) chloride, FeCl solution
The changes are recorded. 3 3+
turns pale green because the iron(III) ions, Fe
are reduced to iron(II) ions, Fe .
2+
B Conversion of iron(III) ion, Fe to iron(II)
3+
4. A dirty green precipitate is formed when
ion, Fe 2+
tested with sodium hydroxide, NaOH solution.
3
1. 2 cm of iron(III) chloride, FeCl solution is This confirms the presence of the iron(II) ions,
3
measured and pour into a test tube. Fe .
2+
2. Half spatula of zinc, Zn powder is added into
the solution in the test tube. Discussion:
2+
3. The mixture is shaken well and warm gently 1. Iron(II) ions, Fe are oxidised to iron(III) ions,
3+
until no further changes. Fe by bromine water, Br .
2
304 1.1.2