Post on 06-Apr-2018
8/3/2019 Master Scoring Chemistry (MRSM KEPALA BATAS) 2011
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Electrolysis in Molten state
1. Molten Lead Bromide contains Lead ionand Bromide ions.
2. Lead ions attracted at cathode. Bromideions attracted at anode.
3. Lead receives two electrons to form Leadmetal. Pb
2++ 2e = Pb. Hence, Grey
precipitate is deposited.
4. Bromide ions attracted at cathode.Bromide donates two electrons to form
Bromine gas. 2Br- = Br2 + 2e. Hence,
Bromine gas is produced at cathode.
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Electrolysis in Aqueous state
1. Copper(II) Sulphate contains Copper(II)ions, Sulphate ions, Hydroxide ions
and Hydrogen ions.
2. Copper(II) ions and Hydrogen ions willbe attracted at cathode. Copper(II)
ions will be selectively discharged
because the position of copper in the
Electrochemical series is lower than
Hydrogen.
3. Sulphate ions and Hydroxide ions willbe attracted to the anode. The
Hydroxide ions will be selectively
discharged because the position of
hydroxide ions in the electrochemicalseries is lower than Sulphate ions.
4. Cu2+ + 2e = Cu5. 4OH- = 2H2O + O2 + 4e6. Full equation : Cu2+ + 4OH- = 2CU +
2H2O + O2
7. The product at cathode is depositionof copper metal while at anode is
effervescence of oxygen gas.
8. For confirmatory test, effervescenceof oxygen gas is tested with glowing
wooden splinter; a rekindle of wooden
splinter is obtained for several
seconds.
8/3/2019 Master Scoring Chemistry (MRSM KEPALA BATAS) 2011
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Arrangement of Cations in Electrochemical Series
K +
Na +
Ca 2+
Mg 2+
Al +Zn 2+
Fe 2+
Sn 2+
Pb 2+
H +
Cu 2+
Hg 2+Ag 2+
Au +
Increasing ability to discharge
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Extraction of Aluminium from
Aluminium Oxide
1. Alimunium oxide (Al2O3) is dissolvedinto melted cryolite (Na3AlF6)
2. The process lower the melting point of C.
3. The electrode are made of graphite.4. In molten state, Aluminium oxide will
dissociate into Al3+
ions and O2-
ions.
5. Al2O3 = 2Al3+ + 3O2-6. At cathode, 4Al3+ + 12e = 4Al7. At anode, 6O2- = 302 + 12e8. The aluminium metal is siphoned to
the ground and Oxygen gas will be
formed.
Purification of Metal
1. The pure copper is placed at cathodeand impure copper is placed at anode.
2. The electrolyte is made of copper-dissolving solution such as Copper(II)
sulphate.
3. At anode, Copper will dissolve to formCopper ions. Cu = Cu
2+
+ 2e4. At cathode, Copper ions will ionize
and accept two electron to form
Copper. Cu2+
+ 2e = Cu
5. The pure Copper will become thickerand the impure Copper will become
thinner.
Electroplating (coating) of Nickel
with Silver
1. Silver is placed at anode while a nickelmaterial ( jug, etc.) is placed at
cathode.
2. The solution is made form silver-dissolving solution such as Silver
nitrate.
3. At anode, the Silver dissolves to formSilver ions. Ag = Ag
++ e
4. At cathode, the Silver ions ionizes andaccept electron to form Silver metal.
Ag+
+ e = Ag
5. The formation of Silver metal willelectroplate (coat) the Nickel material.
6. The thicken of Silver will be stoppeduntil its thick enough.
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Ckg Fys M-Enhancing Technique
Insoluble Soluble
Ca2+
SO42-
Ammonium
Ba2+
Na+
Pb2+
I-
K+
Ag+
Br-
NO3-
Co3-
Cl-
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Alkane
Alkene
Alcohol
Carboxylic
Acid
Ester
Cracking
Dehydration
Al2O3 , H2SO4,
H3PO4
Oxidation
Potassium
Dichromate,
Potassium
Manganate(VI
Hydrogenation
+ H2
Hydration
+ H2O
Esterification
Concentrated
H2SO4
Substitution
+ Cl2
Chloroalkane
CnH2n+1
CnH2n
CnH2n+1OH
CnH2n+1COOH
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