Experiment 13 - STPM

Topic: Electrochemistry – Faraday’s laws

Purpose: To determine the value of Avogadro’s constant by the electrolysis procedure

Materials:
Copper(II) sulphate solution, propanone, 2 pieces of copper plates, 5 connecting wire with crocodiles clips, ammeter, rheostat, switch, 4 dry cells, stop watch, hair dryer, electric balance, wash bottle with distilled water, sand paper, one 250cm3 beaker, one 100cm3 measuring cylinder.

Procedures:
1.    100cm3 of copper(II) sulphate solution is measured using measuring cylinder, then it is poured into a beaker.
2.    2 copper plates are cleaned with sand papers and washed with distilled water before  dried  by hair dryer.
3.    Then, the 2 copper plates were labeled and weighed with electric balance. The mass was recorded in the table below.
4.    The circuit is set up as shown in the diagram.
5.    The circuit is switched on at the same time the stop watch is started.
6.    The rheostat is adjusted so that the current is fixed at 0.5A.
7.    Electrolysis is continued for 30 minutes.
8.    The circuit is switched off and the copper plates are taken out.
9.    The two copper plates are dipped into the distilled water and stirred slightly. For the anode copper, it is rubbed with cloth before wash.
10.    Then, two copper plates are dipped into 100cm3 of propanone and are dried using hair dryer.
11.    The copper plates are weighted with electric balance and the mass is recorded in the table.

Results:
                                       Anode    Cathode
Initial mass/g       
Final mass/g       
Difference in mass/g   
   
 Current= _____________

Time taken= _________________