Engineering
Chemistry
Nernst Equation
Faraday Law
Question

The most popular electrochemical cell, Daniel cell was originally developed by the English chemist John F. Daniel. The general assembly of the cell is as given below

An undergraduate student up a Daniel cell using 100 cm3 of 0.100 M CuSO4 and 0.100 M ZnSO4 solution respectively. The two compartments are connected by suitable salt bridge.

[Given :ECu2+/Cuo=0.34VEZn2+/Zno=0.76V 2.303RTF=0.06,  log 2 = 0.3]

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Linked Question 1

A lab mate of the student asked her for some solid CuCl2. While she was lifting the bottle from a shelf, the lid of the bottle slipped and some amount of CuCl2 fell in the CuSO4 compartment at constant volume. She measured the emf of the cell again and found that it had increased by 9 mV. She used this data to calculate the amount of CuCl2 that had split in the compartment. Calculate the mass of CuCl2 in grams that had split into the Daniel cell? 
(Molecular mass of CuCl2 = 135 g) 

1.35

13.5

27

2.7

Solution

1.109 = 1.100 –0.062log0.1[Cu2+]

[Ci2+] = 0.2 M
Δn = 0.2 × 0.1 – 0.1 × 0.1
= 0.01
w = 0.01 × 135 = 1.35 gm

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Linked Question 2

Calculate the emf (in Volt) of the above cell. Assume the temperature of the laboratory to be 25°C and the solutions are dilute enough so that molar concentrations can be used instead of activities of the solutions.

1.1

0

1.04

1.16

Solution

    E = 1.1 – 0.062log0.10.1

 

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Linked Question 3

After making this calculation, the student discarded the solutions from both the compartments and washed the cell thoroughly. She refilled the compartments with 100 cm3 of the original CuSO4 and ZnSO4 solutions. A current of 0.965 A was drawn from the cell for a period of 20 min.What will be the cell potential after 20 min.? 

1.082 V

1.118 V

1.091 V

1.109 V

Solution

ne =0.965×20×6096500 = 0.012

E = 1.1 – 0.062log0.01+ne20.01ne2

 

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