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Electrochemistry - ISC Class 12 Chemistry Questions with Answers, Page 2

77 past-paper questions on Electrochemistry from ISC Class 12 Chemistry papers (2027-2018), newest first, in full. Questions 21-40 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.

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2025 · 3 marks · Short answerOpen: Answer the following questions: State Kohlrausch’s law of independent migration…
Answer the following questions:
(a)[1.0]
State Kohlrausch’s law of independent migration of ions.
(b)[1.0]
Calculate the molar conductivity of an aqueous solution of $\text{CaCl}_2$ at infinite dilution. The ionic conductance of $\text{Ca}^{2+}$ and $\text{Cl}^-$ ions are $119\cdot0\text{ ohm}^{-1}\text{ cm}^2\text{ mol}^{-1}$ and $76\cdot3\text{ ohm}^{-1}\text{ cm}^2\text{ mol}^{-1}$ respectively.
(c)[1.0]
A galvanic cell has an electrode potential of $1\cdot10\text{ V}$. If an opposing potential of $1\cdot10\text{ V}$ is applied to this cell, what will happen to the cell reaction and the current flowing through the cell?

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2025 · 1 mark · Fill inOpen: Fill in the blanks by choosing the appropriate word(s) from those given in the…
Fill in the blanks by choosing the appropriate word(s) from those given in the brackets: [four, three, remains same, propane, $ns^{1-2}$, increases, six, propan-2-ol, $(n-1)d^{1-10}$, two, decreases, Clemmensen’s, Wolff-Kishner] The molar conductance of a solution ____ on dilution but the specific conductance of a solution ____ on dilution.

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2025 · 3 marks · NumericalOpen: Nandini wants to electroplate her bracelet with silver. She gives the bracelet…
Nandini wants to electroplate her bracelet with silver. She gives the bracelet to an artist.
(a)
After electroplating she gets the information that 1.6117g of the metal is deposited when electric current of 0.2 ampere is passed for 2 hours. How will she make the confirmation that the metal deposited is silver by using the data?
(b)
Which law is applicable to solve the problem?

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2025 · 3 marks · Short answerOpen: Answer the following: Graphical method fails to give the value of molar…
Answer the following:
(a)
Graphical method fails to give the value of molar conductivity at infinite dilution of weak electrolyte. Explain.
(b)
To know the value of molar conductivity at infinite dilution for weak electrolyte, Kohlrausch’s law is effective. Explain.
(c)
Draw the graph to show the variation of molar conductivity of a weak electrolyte with concentration.

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2025 · 2 marks · NumericalOpen: The specific conductivity of acetic acid solution is . Calculate the molar…
The specific conductivity of $0\cdot0025\text{ M}$ acetic acid solution is $7\cdot95 \times 10^{-5}\text{ ohm}^{-1}\text{ cm}^{-1}$. Calculate the molar conductivity of this solution. If molar conductance for acetic acid is $389\cdot5\text{ ohm}^{-1}\text{ cm}^2\text{ mol}^{-1}$ at infinite dilution ($\Lambda^\circ$), what would be its degree of dissociation?

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2025 · 2 marks · Short answerOpen: Yash measures the conductivity of two different solutions of 1M Ethanoic acid…
Yash measures the conductivity of two different solutions of 1M Ethanoic acid and 1M HCl each at $25^\circ\text{C}$.
(a)
Will he observe the same conductivity value for both the solutions? Justify your answer.
(b)
What will be the effect on conductivities when he keeps on diluting the solutions? Explain with the help of a graph.

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2025 · 3 marks · Short answerOpen: Answer the following: What happens to the voltage when the salt bridge is…
Answer the following:
(a)[1.0]
What happens to the voltage when the salt bridge is removed from the two half cells and why?
(b)[1.0]
Copper sulphate solution cannot be stored in a zinc pot. Why?
(c)[1.0]
Why does the density of $\text{H}_2\text{SO}_4$ in a lead storage battery decrease as it is discharged?

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2025 · 1 mark · MCQOpen: The above graph indicates the variation of molar conductivity of different…
The above graph indicates the variation of molar conductivity of different electrolytes. $\text{NaCl}$, $\text{CH}_3\text{COOH}$, $\text{KCl}$ represented as I, II, and III respectively. The order of increase in molar conductivity with concentration is:
  • (a)(II), (III), (I)
  • (b)(I), (III), (II)
  • (c)(III), (II), (I)
  • (d)(III), (I), (II)
Figure for this question

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2025 · 5 marks · Case basedOpen: ‘Freidrich Wilhelm Georg Kohlrausch was a German physicist who studied the…
‘Freidrich Wilhelm Georg Kohlrausch was a German physicist who studied the electrical conductivity of electrolytic solutions. From 1875-1879 he performed numerous experiments with aqueous solutions of different salts, acids and other electrolytes. He concluded that each type of migrating ion has a specific conductivity, and it does not depend on the origin of the ion. In a simple way, his conclusions were applicable to strong electrolytes as well as more complex behaviour was observed for weak electrolytes.’ Source: https://doi.org/10.1002/elsa.202160008
(a)[1.0]
What did Kohlrausch mean when he said that each ion has specific conductivity which is independent of origin of ions?
(b)[2.0]
Explain the law proposed by Kohlrausch with example.
(c)[2.0]
How do you propose to calculate the molar conductivity of a weak electrolyte (acetic acid) by using his law?

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2025 · 3 marks · Short answerOpen: Geet has set-up the following galvanic cell by taking the electrolyte solution…
Geet has set-up the following galvanic cell by taking the electrolyte solution of $\text{Pb}(\text{NO}_3)_2$ and $\text{CrCl}_3$. $E^\circ = -0.13\text{ V}$ $E^\circ = -0.74\text{ V}$
Figure for this question
(a)
How will you design the feasible cell by taking appropriate salt solution in place of solution A and B?
(b)
What is the applicability of the above cell?
(c)
Consider, salt bridge is filled with Potassium Chloride (KCl) solution. How does salt bridge maintain electrical neutrality?

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2025 · 2 marks · NumericalOpen: Sudeshna took her gold plated bangles to a goldsmith for cleaning and…
Sudeshna took her gold plated bangles to a goldsmith for cleaning and electroplating as they had become black due to constant exposure to dust and dirt. Calculate the amount of charge in coulombs needed for plating $1\cdot0\text{ g}$ of gold on the bangles. During electroplating, the following reaction takes place: $\text{Au}^{3+} + 3\text{e}^- \longrightarrow \text{Au}$ (Given: Atomic weight of $\text{Au} = 197\text{ g mol}^{-1}$)

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2025 · 3 marks · Short answerOpen: Answer the following questions: Specific conductance of a solution decreases…
Answer the following questions:
(a)[1.0]
Specific conductance of a solution decreases upon dilution. Why?
(b)[1.0]
The emf of a cell should be positive for a spontaneous reaction. Give a reason.
(c)[1.0]
Name the type of cell in which reaction occurs only in one direction and cannot be reversed by an external energy source. Write any one disadvantage of this type of cell.

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2025 · 1 mark · Fill inOpen: Choose the appropriate word(s) from the bracket [+2, ethane, tetrahedral…
Choose the appropriate word(s) from the bracket [+2, ethane, tetrahedral, square planar, zero, dry cell, nickel-cadmium cell, propane, Wolff-Kishner, Stephen, completely filled, incompletely filled, paramagnetic, diamagnetic]: ____ is an example of a primary cell but ____ is an example of a secondary cell.

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2025 · 2 marks · Short answerOpen: Rohan arranged three coulometers in series and passed one faraday of charge for…
Rohan arranged three coulometers in series and passed one faraday of charge for a definite time to all three electrolytes as shown in the picture given below:
Figure for this question
(a)
What will be ratio of number of moles of positive ions liberated at cathode in each coulometer?
(b)
If he passed 4825 coulombs of charge through the electrolytes, how many gram-equivalent of copper will be deposited at the cathode?

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