Everything Science Grade 12

CHAPTER 4. ELECTROCHEMICAL REACTIONS 4.3

Item Galvanic cell Electrolytic cell

Metals used for electrode Two metals with different re-

action potentials are used as

electrodes

The same metal can beused

for both the cathode and the

anode

Charge of the anode negative positive

Charge of the cathode positive negative

The electrolyte solution(s) The electrolyte solutions are

kept separate from one an-

other, and are connectedonly

by a salt bridge

The cathode and anodeare in

the same electrolyte

Energy changes Chemical potential energy

from chemical reactions is

converted to electrical energy

An external supply of electri-

cal energy causes a chemical

reaction to occur

Applications batteries, electroplating Electrolysis e.g. of water,NaCl

Table 4.1: A comparisonof galvanic and electrolytic cells

Exercise 4 - 3

1. An electrolytic cell consists of two electrodesin a silver chloride (AgCl) solution,
   connected to a source of current. A current is passed through the solution and
   Ag+ions are reduced to a silver metal deposit on one of the electrodes.

(a) Give the equation for the reduction half-reaction.

(b) Give the equation for the oxidation half-reaction.

2. Electrolysis takes place in a solution of molten lead bromide (PbBr)to produce
   lead atoms.

(a) Draw a simple diagram of the electrolytic cell.

(b) Give equations for the half-reactions that take place at the anode and cath-

ode, and include these in the diagram.

(c) On your diagram, show the direction in which current flows.

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