Name:
Class:
Subject: Unit 4 Electochemistry
Date
:
Term/Year
: Term 3 – 2024/2025
Answer all questions. (Total: 16 marks)
1
Molten lead (II) bromide is electrolysed as shown.
Which ions are discharged at each electrode?
positive electrode
2
negative electrode
A
+
Pb
Br2-
B
Pb2+
Br-
C
Br2-
Pb+
D
Br-
Pb2+
Which of these elements could be formed at the anode when a molten salt is electrolysed?
A copper
B iodine
C lithium
D strontium
3
Which statement about the electrolysis of molten lead (II) bromide is correct?
A A colourless gas is seen at the cathode.
B A grey metal is seen at the anode.
C A red / brown gas is seen at the anode.
D A red / brown metal is seen at the cathode.
1
4
When concentrated sodium chloride solution is electrolysed, elements X and Y are formed.
What are X and Y?
5
X
Y
A
chlorine
hydrogen
B
hydrogen
chlorine
C
hydrogen
oxygen
D
oxygen
hydrogen
Substance X was electrolysed in an electrolytic cell.
A coloured gas was formed at the anode and a metal was formed at the cathode.
What is substance X?
A aqueous sodium chloride
B molten lead bromide
C molten zinc oxide
D solid sodium chloride
2
(0653 Science – Combined November 2021 QP 42)
6
A student uses inert electrodes for the electrolysis of dilute aqueous sodium chloride and
concentrated aqueous sodium chloride solutions.
(a)
State what is meant by inert.
……………………………………………………………………………………………………...
……………………………………………………………………………………………………...
[1]
(b) For each solution, the products formed at the positive and negative electrodes are gases.
The student tests the gases.
Table 6.1 shows the observations.
Table 6.1
Use the observations in Table 6.2 to identify the gases formed at the positive and negative
electrodes for each solution.
Complete Table 6.2 with the names of these gases.
Table 6.2
[3]
(c)
Molten sodium chloride is electrolysed using inert electrodes.
Describe how sodium is formed from sodium ions during electrolysis.
……………………………………………………………………………………………………...
……………………………………………………………………………………………………...
……………………………………………………………………………………………………...
3
[3]
7
Hydrogen can also be manufactured by electrolysis. The electrolyte is concentrated aqueous
sodium chloride. The electrodes are inert.
The products of electrolysis are hydrogen, chlorine and sodium hydroxide.
(a)
Define electrolysis.
……………………………………………………………………………………………………...
……………………………………………………………………………………………………...
[2]
(b) Name a substance that can be used as the inert electrodes.
……………………………………………………………………………………………………...
(c)
[1]
Describe the observation for chlorine.
……………………………………………………………………………………………………...
4
[1]