Hypothesis
I predict that the longer the current is passed through the circuit for the electrolysis of copper, the more mass decrease there will be at the anode. The mass of copper collected at the cathode will increase, however. This is because more energy is present, so the number of ions in the electrolyte (copper sulfate solution) will increase, and also, the rate of electrolysis will increase. Copper sulfate (CuSO4) is made up of 4 ions; Copper (II) ions (Cu2+), Sulphate ions (SO42-), Hydrogen ions (H+), and Hydroxide ions (OH-). The Copper (II) and the Hydrogen ions are positively charged, and the Hydroxide and sulfate ions are negatively charged. Negatively charged ions are attracted to the positive electrode- the anode- and the positively charged ions are attracted to the negative electrode- the cathode. The copper ions are less reactive than the hydrogen ions in the reactivity series, so need more electrons, which means they gain more than the hydrogen. Therefore they will attract to the cathode, and the hydroxide ions will attract to the anode as they are more reactive than the sulfate ions. So they will give up their electrons faster, also losing fewer ions than those of the sulfate ions. This can be seen in the half-ionic equations below.
At the cathode: Cu2+ (aq) + 2e- Cu (s) At the anode: 4OH- 2H2O + O2 +4e- At the anode, neither hydroxide ions nor sulfate ions are discharged. This is because the type of electrodes used affects what happens at the anode. Instead, copper atoms from the anode lose electrons to become copper (II) ions. The mass of the anode decrease as copper dissolves.
Cu (s) Cu2+ (aq) + 2e-
Oxidation occurs = Copper atoms lose electrons Over time, pure copper is transferred from the anode to the cathode. Anode decreases in mass whilst the cathode increases in mass. The impurities at the anode all off to the bottom of the beaker/bath, forming sludge.
Apparatus-
100ml glass beaker, the solution will be poured into this beaker to a certain amount 3x Crocodile clips to connect the circuit Stopwatch to time how long the anode will be in the copper sulfate solution (hh. mm. ss) Tissue to dry the anode 50ml Copper Sulphate solution electrolysis will occur Ammeter to measure current (to 2 decimal places) Voltmeter to measure voltage (to 2 decimal places) Power supply (12W) to supply electricity Copper Anode Copper Cathode Measuring cylinder to measure how much copper sulfate solution will be used Rheostat to control the amount of current flowing Fair Test It is important to make sure the test is a fair one by keeping certain factors the same. This outlines any anomalies from occurring, and hence the data is more reliable.
This is what needs to be kept the same:
The amount of copper sulfate used Time the reaction will take will have to be kept constant The apparatus Weigh the anode before and after every experiment so it is known how much copper has been deposited In order to ens...
