When the engine of a vehicle containing a lead–acid battery is running, the lead–acid battery is charged up by the following reactions:
anode: PbSO4(s) + 2H2O(l) → PbO2(s) + 2e−+ 4H+
(aq) + SO42− (aq)
cathode: PbSO4(s) + 2e− → Pb(s) + SO42− (aq)
Lead(II) sulfate occurs as an insoluble coating on the surface of both metal electrodes.
1
1
Question 1
1.
Question 2
2.
Question 3
3.
a What is the purpose of the salt bridge?
Question 4
4.
b Give equations for the reactions in each half-cell
Question 5
5.
c What changes would be observed in each beaker?
Question 6
6.
.Copy and Label the diagram to show the following:
● the direction of electron flow through the external circuit
● the anode
● the cathode
● the positive electrode
● the negative electrode
● the direction of ion flow in the salt bridge
Question 7
7.
a What is the single vertical line used to represent?
Question 8
8.
b What is the double vertical line used to represent?
Question 9
9.
c What are the two electrodes made from in this
cell?
Question 10
10.
d Give the half-equations occurring at each
electrode.
Question 11
11.
e Give the overall equation for the cell.
Use the activity series in the IB data book to put the following voltaic cells in increasing order of the voltage they produce. Assume that any differences in conditions, such as concentration and temperature, can be ignored.
A Zn2+ + Mg → Mg2+ + Zn
B 2Cr3+ + 3Zn → 2Cr + 3Zn2+
C 3Mg2+ + 2Cr → 2Cr3+ + 3Mg
A<B<C
B<A<C
C<A<B
A<C<B
B<C<A
C<B<A
a Rechargeable batteries can be both chargedand discharged. What do these two terms mean?
Question 15
15.
Question 16
16.
Question 17
17.
Question 18
18.
Question 19
19.
Question 20
20.
a Give the equations when the lead–acid battery is being discharged.
Question 21
21.
b Using the equations, identify a suitable electrolyte in a lead–acid battery.
In a simple voltaic cell made from two metals and solutions of their ions, would the metal higher in
the activity series form the anode or the cathode of the cell?
Anode
Cathode
In a voltaic cell, in which direction do the electrons
flow in the external circuit?
from anode to cathode
from cathode to anode
through the salt bridge
through the electrolyte
b In a rechargeable battery, does oxidation occur at the anode or cathode when the cell is being discharged?
anode
cathode
c In a rechargeable battery, does oxidation occur at the anode or cathode when the cell is being charged?
anode
cathode
d When a rechargeable battery is being discharged, is the anode negative or positive?
negative
positive
e When a rechargeable battery is being charged, is the anode negative or positive?
negative
positive
f Electrons flow in the external part of an electrochemical cell. What type of particle moves through the electrolyte of a cell?
