Unit 13 - Applications of Inorganic Chemistry - Assignment B (Distinction)

Measuring cell potentials


Aim

The purpose of this experiment is to construct three electrochemical cells, and to measure the
potential difference between the electrodes, noting the polarity.


Introduction

You will construct the cells given below according to the method and measure the potential
difference between the metal electrodes using a high resistance voltmeter.

o Zn(s) | Zn2+(aq) ¦¦ Cu2+(aq) | Cu(s)
o Zn(s) | Zn2+(aq) ¦¦ Pb2+(aq) | Pb(s)
o Pb(s) | Pb2+(aq) ¦¦ Cu2+(aq) | Cu(s)


When measuring the potential difference between the electrodes of each cell, the polarity of
each electrode is indicated by the positive sign and negative sign on the voltmeter (or red and
black terminals respectively). Thus, you can determine at which electrode electrons are needed
and at which electrode electrons are produced. From this, you can work out the direction in
which the overall reaction proceeds.

Diagram

high resistance
voltmeter




V



salt bridge




metal
strip



metal ion
solution




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