that dips into an aqueous solution of copper sulphate taken in a beaker, as shown in Figure . . Joining the half cells The zinc and copper strips are externally connected using a wire through a switch (k) and a load (example: volt meter). The electrolytic solution present in the cathodic and anodic compartment are connected using an inverted U tube containing agar-agar gel mixed with an inert electrolytes such as KCl, Na SO etc., The ions of inert electrolyte do not react with other ions present in the half cells and they are not either oxidised (or) reduced at the electrodes.
The solution in the salt bridge cannot get poured out, but through which the ions can move into (or) out of the half cells. When the switch (k) closes the circuit, the electrons flows from zinc strip to copper strip. This is due to the following redox reactions which are taking place at the respective electrodes. XII U9 Electro XII U9 Electro - - - - Digital voltmeter .
Salt bridge Na SO (aq) (Na + ) Zn(s) Zn + (aq) + 2e − Cu + (aq) + 2e − Cu (s) 2e - 2e - Zn (Zn + +SO - ) ( Cu + +SO - ) SO - Zinc (anode) Cu SO - Zn + e - Copper (cathode) CuSO (aq) e - Cu Cu Cu 2e Zn Zn Zn 2e Cu + ZnSO (aq) Figure . : Daniel cell Anodic oxidation The electrode at which the oxidation occurs is called the anode. In Daniel cell, the oxidation take place at zinc electrode, i.e., zinc is oxidised to Zn + ions by loosing its electrons. The Zn + ions enter the solution and the electrons enter the zinc metal, then flow through the external wire and then enter the copper strip.
Electrons are liberated at zinc electrode and hence it is negative ( - ve). Zn(s) Zn (aq) + 2e (los + s of electron-oxidation) Cathodic reduction As discussed