Chapter 18 Electrolysis

1
electric cells
a simple electric cell

• a simple electric cell consists of two different
  metal electrodes placed in an electrolyte
• metals high up in the reactivity series give up
  electrons more readily negative electrode in the
  cell
• metals low down in the reactivity series will be
  the positive electrode in the cell

• voltage of electric cell depends on the positions
  of the two metals in the reactivity series the
  farther apart they are, the higher the voltage
• use of electric cell portable energy such as
  batteries

portable energy batteries
2
electric cells
a simple electric cell

• consists of pieces of Cu and Zn metals in a
  solution of NaCl
• zinc being more reactive than Cu is the negative
  electrode Cu metal is the positive electrode

zinc metal (negative electrode)
voltmeter
-

copper metal (positive electrode)
NaCl(aq)
3
electric cells
a simple electric cell

• at the Zn electrode, Zn atoms give up electrons
  to form Zn2 ions

Zn(s) Zn2(aq) 2e-

• at the Cu electrode, Cu2 ions take in electrons
  to give Cu atoms

Cu2(aq) 2e- Cu(s)

• overall reaction

Zn(s) Cu2(aq) Zn2(aq) Cu(s)
4
positive ions
are
form
cations
metals or H2
an example is
Cr-plating
are discharged at
are produced at
electroplating
cathode
ionic compound (molten/solution)
is used in
gives electrons to
moving ions
carry the current in
is negative electrode in
contains
is
decomposes
battery
electrolysis
electrolyte
is used to extract
is positive electrode in
takes electrons from
reactive metals
is used to refine
anode
are discharged at
an example is
are produced at
copper
non-metals
anions
aluminium
are
form
negative ions