Question

As part of your preparation for performing this experiment, calculate the volume of 1 M metal ion solution that needs to be diluted (and what the final volume of the diluted solution should be) in order to prepare the solution required for creating a cell with a potential of exactly 0.5 V. Record this information in your lab notebook and check the accuracy with your TA before preparing the solution.

A) Cu/Cu²⁺ and Pb/Pb²⁺
B) Zn/Zn²⁺ and Cu/Cu²⁺
C) Zn/Zn²⁺ and Pb/Pb²⁺
D) none of these

Answer 1

Answer, -

A ) Cu/ Cu 2+ and Pb / Pb 2+

Explanation ,

The answer to this question calls for following steps,

1.Calculate the standard emf of standard cell constructed by the given half cells.

2. apply Nernst equation to calculate the ratio of salt concentrations,

3. calculate the required dilution of given 1 M solution .

............It is with the cell at "A) " with calculated* E^o_cell   = 0.47 V in which a suitable dilution

of metal solution can provide an E_cell   = 0.5 V ,

according to Nernst equation-

.......E_cell   = E^o_cell   + ( 0.059 /2 ) log ( [ Pb2+] / [ Cu 2+ ] )

.....Substituting the values we get,

.........0.50 = 0.47 + ( 0.059 / 2 ) log ( [ Pb 2 + ] / [ Cu 2+ ] )

therefore , [ Pb 2 + ] / [ Cu 2 + ] = antilog{( 0.03 x 2 ) / 0.059 }

.......................................................... = 10.3979

....Hence , 1M metal ion solution should be diluted to give the concentrations as

[ Pb 2+ ] / [ Cu 2+ ] = 10.39 79 / 1

However, the practical accuracy should be checked as desired in the experiment.

* the cell potential is calculated using standard electrode potentials.