Electrochemical cells
Aim
To examine the work of electrochemical cells; to determine the electromotive force (emf) generated in different galvanic cells and define the effect of various factors to the emf. Introduction
The electrochemical cell is a system of two electrodes immersed in a solution of their salts. There are two types of electrochemical cells: Galvanic or Voltaic cells Electrolytic cells
A galvanic cell is consisted of two half-cells containing electrodes connected by an external circuit and a salt bridge. Cells use the electrodes which provide electrical connection between half-cells. Oxidation occurs in the anode; the reduction occurs in the cathode. A salt bridge is used to keep reaction continuing by ensuring electrical…show more content… Discussion
In the reaction between zinc and copper sulphate solution, the copper separated from the solution as a precipitate. In addition, the changing color of the solution means that the copper sulphate was not there anymore. Active metal zinc replaced the copper in the sulfate and formed a salt. The zinc is oxidized, and copper is reduced.
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
Redox reactions by the ion-electron method:
Cu2+ + 2e- → Cu
Zn → Zn2+ + 2e-
Net ionic equation:
Zn (s) + Cu2+ (aq) → Cu (s) + Zn2+ (aq)
Cu2+ is the oxidizing agent in the reaction, because its oxidation state +2 in Cu2+(aq) drops to 0 in Cu(s) gaining two electrons.
In the experiment with Fe2+, the polarity of iron is different in each cells. In the zinc/iron cells, Fe2+ acted as cathode, because the standard reduction potential for iron is more positive than that of zinc. That is why, iron metal will gain electrons from zinc ions reducing an oxidation state. But in the iron/copper cells, Fe2+ acted as anode, because the standard reduction potential for iron is more negative than that of copper. Therefore, iron will lose electrons to copper generating positive electrical