Chemistry Reference
In-Depth Information
Checklist
After studying Chapter 5 you should know and understand the
following terms.
•
Anions
Negative ions; these are attracted to the anode.
•
Anode
The positive electrode. It is positively charged
because electrons are drawn away from it.
•
Cathode
The negative electrode. It is negatively charged
because an excess of electrons move towards it.
•
Cations
Positive ions; these are attracted to the cathode.
•
Electrode
A point where the electric current enters and
leaves the electrolytic cell. An inert electrode is usually
made of platinum or carbon and does not react with the
electrolyte or the substances produced at the electrodes
themselves.
•
Electrolysis
A process in which a chemical reaction is
caused by the passage of an electric current.
•
Electrolyte
A substance which will carry electric current
only when it is molten or dissolved.
•
Electroplating
The process of depositing metals from
solution in the form of a layer on other surfaces such as
metal or plastic.
•
Hall-Héroult cell
The electrolysis cell in which aluminium
is extracted from purifi ed bauxite dissolved in molten
cryolite at 900 °C. This cell has both a graphite anode and a
graphite cathode.
•
Inert electrode
These are electrodes that do not react
with the products of electrolysis, e.g. carbon, platinum.
•
Membrane cell
An electrolytic cell used for the
production of sodium hydroxide, hydrogen and chlorine
from brine in which the anode and cathode are separated
by a membrane.
•
Oxidation
Takes place at the anode and involves a
negative ion losing electrons.
•
Reduction
Takes place at the cathode and involves a
positive ion gaining electrons.
Questions
1
The leaf in Figure 5.22 has been copper plated. Suggest a
suitable method for copper plating the leaf.
2
Explain why copper(ii)
ii
) chloride solution would not be
used as an electrolyte in the electrolyte cell used for
copper plating.
3
Write equations which represent the discharge at the
cathode of the following ions:
a
K
+
b
Pb
2
+
c
Al
3
+
and at the anode of:
d
Br
−
e
O
2−
f
F
−
