Problem solving tips

## Electrochemistry

- Want to score better marks in exams? Have a look at some problem solving tips.
1
Tip: Follow these simple tips to get the problems related to Nernst equation right:
• Write the formula relating the quantities asked in the question
• Write down all the values given in the question
• Plug in the values into the formula and obtain the value asked in the question
• Be careful to use the value of R, T ,n and F as variation in their values can give a completely different answer
Now get on to solve these questions:

Calculate EMF of

A
1.56V
B
2.36V
C
0.236V
D
0.118V
For a reaction, , has been found to be . The is:
A
B
C
D
none of these
For hydrogen-oxygen fuel cell, the cell reaction is:

If , then emf of this cell is:
A
B
C
D
2
Tip: Follow these simple tips to get the problems asking you to calculate limiting molar conductivities of weak electrolytes using kohlrausch law
• Express the molar conductivities of electrolytes given in the question as the sum of conductivities of individual ions according to the kohlrausch law
• Number them as equations 1,2,3... and so on
• Try to find a mathematical link between these equations to arrive at the ions whose sum will you the molar conductivities of the weak electrolyte.
• Be careful in doing the addition, subtraction or multiplication, as an error in calculations is the biggest cause of loss of marks in these type of problems
Now get on to solve these questions:
If the values of of and are and respectively, the of in is:
A
B
C
D
At , the molar conductances at infinite dilution for the strong electrolytes and are and respectively, in is
A
B
C
D
3
Tip: Follow these simple tips to get the problems related to faraday's law of electrolysis
• First write down the reactions for the electrolytic reduction to get to know the number of electrons required for it.
• Calculate the amount of current required for the required amount of ion to get discharged.
• Use unitary method to calculate the amount of metal that will be deposited at the cathode according to the information given and calculated by you
• Be careful while calculating the amount of current, as the time should always be converted into seconds if not already given.
Now get on to solve these questions:

The number of electrons participating in the electrode reaction when one atomic weight of a bivalent metal was deposited at the cathode:

A
9.65 x 10
B
0.6 x 10
C
12.04 x 10
D
3.01 x 10

Three Faradays of electricity was passed through an aqueous solution of magnesium bromide. The weight of magnesium metal deposited at the cathode in grams is:

A
56
B
84
C
36
D
168