Chemistry Investigatory Project
Tanmay 12-D
Aim: To study the EMF of Daniel cell under various factors
such as change in temperature, concentration and area of
electrodes
Material Required: Two beakers, copper rode, zinc
rode, KCl solution, cotton cloth, voltmeter, distilled water,
connecting wires and 1M, 0.1M and 0.01M of CuSO4 and
ZnSO4
Theory:
When an external circuit is connected, the
chemical reaction
For the anode half-cell is:
Zn(s) Zn2+(aq) + 2e-
For the cathode half-cell is:
Cu2+(aq) + 2e- Cu(s)
Therefore, the overall reaction of the Daniel Cell:
Zn(s)+Cu2+(aq) Zn2+(aq) + Cu(s)
Features of Daniel Cell are:
Zinc rod at which oxidation occurs is called anode while
Cu rod at which the reduction takes is called cathode.
Overall rxn occurring in the electrochemical cell is due
to two half-cell rxn, one occurring in each beaker
The two half-cell rxns always take place simultaneously
Since electrons are produced at Zn electrode being rich
in electrons and pull these electrons into external
circuit & hence acts a -ve pole. The Cu electrode on other
hand being deficient in electrons acts as +ve pole.
Electrons flow from -ve pole to +ve pole in external
circuit, however conventionally current is said to flow in
opposite direction.
Concentration of CuSO4 soln decreases with passage of
time as cell operates, consequently the current fall with
passage of time.
Salt bridge:
It completes the electric circuit by allowing
the solution to flow from one solution to another without
mixing the two solutions and maintains the electronegativity
of the solutions in the two half cells.
Electromotive force of cell(EMF):
Electromotive force, also called emf, is
the voltage developed by any source of
electrical energy such as a battery or
dynamo. It is the energy transferred to
an electric circuit per unit of electric
charge, measured in volts
Procedure:
Take two beakers and pour the required chemicals in
resp. beaker and mark them for identification.
Take two square to slide in and connecting wire to their
screw
Connecting -ve of voltmeter to anode and its +ve to
cathode.
Take the filter paper long enough to dip into both
solutions. Dip the filter paper in KCL soln. and put it as
salt bridge.
Put electrode voltmeter set up. Note the reading quickly
and then put of electrode voltmeter set up.
For measuring variations with change in concentration
of the electrolyte, use electrolyte of different molarity
and note the readings
For measuring variations with change in temperature of
electrolyte heat the solutions, put on the set up of
electrode voltmeter and noted the reading.
Observation Table:
1)Variation with Concentration:
At a fixed Temperature = 28C
Molarity of Molarity of Voltmeter
CuSO4(M) ZnSO4(M) reading(V)
1M 1M
0.1M 0.1M
0.01M 0.01M
2)Variation with Temperature:
At a fixed concentration: 1M
Temperature of Temperature of Voltmeter
CuSO4(aq) ZnSO4(aq) reading (V)
Result:
1M concentration of CuSO4 and ZnSO4 gives __ V, then 0.1M
gives __V and finally 0.01M gives __V showing that as the
molarity decreases the EMF of cell increases.
Precautions:
Handle chemicals with care and safety as Zn and Cu are
toxic.
Sand the Zn and Cu electrolyte with sand before using
them to ensure clean and accurate readings
Take the reading from voltmeter after it get stable
Connect the positive terminal of voltmeter with copper
electrode and vice versa with Zinc electrode.
Ensuring that the KCl used as salt bridge doesn’t leak
into half-cell.
Keep the apparatus clean so that the chemicals don’t get
contaminated
