Determination of EMF of a Cell

Materials required

The Procedure

Real Lab Procedure

  • Take two clean beakers.
  • In one beaker take 1 M copper sulphate solution and in the other take 1 M zinc sulphate solution.
  • Take a copper strip and clean it using a sand paper.
  • Dip the copper strip into the beaker containing the 1 M copper sulphate solution.
  • Similarly, take a zinc strip and clean it using a sand paper.
  • Then dip it into the beaker containing 1 M zinc sulphate solution.
  • Take a salt bridge and connect the two solutions using the salt bridge.
  • Take a voltmeter and connect the copper strip to the positive terminal and the zinc strip to the negative terminal using connecting wires.
  • Note the position of the pointer in the voltmeter and record the reading.
  • Repeat the experiment by taking different concentrations of zinc sulphate and copper sulphate solutions.

Simulator Procedure (as performed through the Online Labs)

  • You can select the temperature using the slider.
  • You can select the anode from ‘Select Electrode’ dropdown list.
  • You can select the concentration of the electrolyte in the anodic part using the slider.
  • Now, select the cathode from ‘Select Electrode’ dropdown list.
  • To select the concentration of the electrolyte in the cathodic part use its slider.
  • You can see the value of emf of each cell on the voltmeter.
  • You can also see the chemical reactions and the equation to calculate the EMF of the cell on the left side menu.
  • To redo the experiment anytime, click on the ‘Reset’ button.

Observations 

Concentration of ZnSO4 solution (M) Concentration of CuSO4 solution (M) EMF of the Cell (V)
1 M 1 M  
1 M 0.5 M  
1 M 0.025 M  
1 M 0.0125 M  
0.5 M 1 M  
0.025 M 1 M  
0.0125 M 1 M  

Conclusion

EMF of the cell increases with decrease in concentration of the electrolyte around the anode and increase in concentration of the electrolyte around cathode.

Precautions

  • The concentration of copper sulphate and zinc sulphate should neither be too low nor too high.
  • Clean the zinc strip and copper strip with sand paper before use.
  • Connect the copper strip to the positive terminal and the zinc strip to the negative terminal of the voltmeter.
  • The two half cells should be connected using a salt bridge.
  • Note the reading only when the pointer becomes stable.  

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