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Electrochemistry - ISC Class 12 Chemistry Questions with Answers, Page 3

77 past-paper questions on Electrochemistry from ISC Class 12 Chemistry papers (2027-2018), newest first, in full. Questions 41-60 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.

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2025 · 1 mark · Fill inOpen: Choose the appropriate word(s) from the bracket [ethanol, [Fe(H2O)6]2+, anode…
Choose the appropriate word(s) from the bracket [ethanol, [Fe(H2O)6]2+, anode, d2sp3, Cannizzaro, reducing, cathode, sp3d2, iodine, [Fe(CN)6]4-, methanol, aldol, oxidising, manganese dichloride]: In electrochemical cells, the electrode having negative values of standard reduction potential acts as ____ while the electrode possessing positive values of standard reduction potential acts as ____.

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2025 · 3 marks · Short answerOpen: Answer the following questions: What should be the sign (positive or negative)…
Answer the following questions:
(a)[1.0]
What should be the sign (positive or negative) for $E^\circ_{\text{cell}}$ and $\Delta G^\circ$ for a spontaneous redox reaction occurring under standard conditions?
(b)[1.0]
Why does molar conductance ($\Lambda_m$) of $\text{CH}_3\text{COOH}$ increase drastically on dilution, while that of $\text{KCl}$ increases gradually?
(c)[1.0]
How much charge is required in coulombs for the complete reduction of $1\text{ mol}$ of $\text{Cu}^{2+}$ to $\text{Cu}$?

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2025 · 2 marks · NumericalOpen: Calculate the value of , and that can be obtained from the following cell at …
Calculate the value of $E^\circ_{\text{cell}}$, $E_{\text{cell}}$ and $\Delta G$ that can be obtained from the following cell at $298\text{ K}$. $\text{Al}/\text{Al}^{3+}(0\cdot01\text{M}) \parallel \text{Sn}^{2+}(0\cdot015\text{M})/\text{Sn}$ Given $E^\circ_{\text{Al}^{3+}/\text{Al}} = -1\cdot66\text{ V}$; $E^\circ_{\text{Sn}^{2+}/\text{Sn}} = -0\cdot14\text{ V}$

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2024 · 5 marks · NumericalOpen: Calculate the value of and that can be obtained from the following cell under…
Figure for this question
(a)[3.0]
Calculate the value of $E^\circ_{\text{cell}}$ and $\Delta G^\circ$ that can be obtained from the following cell under the standard conditions at $25^\circ\text{C}$: Given $E^\circ_{(\text{Zn}^{2+}/\text{Zn})} = -0\cdot76\text{ V}$; $E^\circ_{(\text{Sn}^{2+}/\text{Sn})} = -0\cdot14\text{ V}$ $1\text{ Faraday} = 96500\text{ C mol}^{-1}$
(b)[2.0]
How much electricity in Faraday is required for the complete reduction of $\text{MnO}_4^-$ ions present in $500\text{ ml}$ of $0\cdot5\text{ M}$ solution to $\text{Mn}^{2+}$?

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2024 · 1 mark · MCQOpen: Which one of the following statements is correct regarding the dry cell? (P)…
Which one of the following statements is correct regarding the dry cell? (P) Zinc container acts as an anode in dry cell. (Q) Zinc container touches the paste of $\text{MnO}_2$ and carbon. (R) Dry cell can be charged easily. (S) Graphite rod acts as a cathode in dry cell.
  • (a)Only (P) and (R)
  • (b)Only (Q) and (R)
  • (c)Only (P) and (S)
  • (d)Only (Q) and (S)

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2024 · 1 mark · Assertion-reasonOpen: Specific conductivity of all electrolytes decreases on dilution.

Assertion: Specific conductivity of all electrolytes decreases on dilution.

Reason: On dilution, the number of ions per unit volume decreases.

  • (a)Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
  • (b)Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
  • (c)Assertion is true but Reason is false.
  • (d)Assertion is false but Reason is true.

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2024 · 2 marks · Short answerOpen: A rusted piece of iron undergoes electrochemical reactions. Write the chemical…
(i)[1.0]
A rusted piece of iron undergoes electrochemical reactions. Write the chemical reaction taking place at: (a) the electrode that behaves as an anode. (b) the electrode that behaves as a cathode.
(ii)[1.0]
Given that the standard reduction potential for $\text{Al}^{3+}/\text{Al} = -1\cdot66\text{ V}$ and $\frac{1}{2}\text{I}_2/\text{I}^- = 0\cdot54\text{ V}$, what will be the standard potential of the cell made by using $\text{Al}^{3+}$ and $\text{I}^-$?

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2024 · 1 mark · Assertion-reasonOpen: Adding water to two beakers ‘A’ and ‘B’ containing and solutions respectively…

Assertion: Adding water to two beakers ‘A’ and ‘B’ containing $\text{NaOH}$ and $\text{CH}_3\text{COOH}$ solutions respectively will increase the molar conductance ($\Lambda_m$) of the solutions sharply in beaker ‘A’ and slowly in beaker ‘B’.

Reason: Molar conductance ($\Lambda_m$) increases with a decrease in concentration or upon dilution.

  • (a)Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
  • (b)Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
  • (c)Assertion is true but Reason is false.
  • (d)Assertion is false but Reason is true.

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2024 · 2 marks · NumericalOpen: Calculate the maximum possible electrical work that can be obtained from a…
Calculate the maximum possible electrical work that can be obtained from a galvanic cell under standard conditions at $298\text{ K}$. $\text{Zn} \mid \text{Zn}^{2+}_{(\text{aq})} \parallel \text{Ag}^+_{(\text{aq})} \mid \text{Ag}$ Given $E^\circ_{(\text{Zn}^{2+}/\text{Zn})} = -0\cdot76\text{ V} \text{ ; } E^\circ_{(\text{Ag}^+/\text{Ag})} = +0\cdot80\text{ V}$

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2024 · 5 marks · Short answerOpen: The molar conductivity vs curve for , , and are shown below in random order…
Figure for this question
(a)[3.0]
The molar conductivity vs $\sqrt{C}$ curve for $\text{Na}_2\text{SO}_4$, $\text{H}_2\text{SO}_4$, and $\text{NH}_4\text{OH}$ are shown below in random order. Identify the curve that corresponds to $\text{Na}_2\text{SO}_4$, $\text{H}_2\text{SO}_4$, and $\text{NH}_4\text{OH}$. Justify your answer.
(b)[2.0]
The molar conductivity ($\Lambda_m$) of a dilute solution of methanoic acid is $34\cdot1\text{ S cm}^2/\text{mol}$. Calculate its degree of dissociation. (Given $\lambda^0(\text{H}^+) = 349\cdot6\text{ S cm}^2/\text{mol}$ and $\lambda^0(\text{HCOO}^-) = 54\cdot6\text{ S cm}^2/\text{mol}$)

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2024 · 5 marks · NumericalOpen: Study the diagram given below that represents Cu-Ag electrochemical cell and…
(a)[3.0]
Study the diagram given below that represents Cu-Ag electrochemical cell and answer the questions that follow. Given $E^\circ_{(\text{Cu}^{2+}/\text{Cu})} = 0\cdot337\text{ V} \text{ ; } E^\circ_{(\text{Ag}^+/\text{Ag})} = 0\cdot799\text{ V}$ (1) Write the cell reaction for the above cell. (2) Calculate the standard emf of the cell. (3) If the concentration of $[\text{Cu}^{2+}]$ is $0\cdot1\text{ M}$ and $E_{\text{cell}}$ is $0\cdot422\text{ V}$, at $25^\circ\text{C}$, calculate the concentration of $[\text{Ag}^+]$. (4) Calculate $\Delta G$ for the cell.
Figure for part (a)
(b)[2.0]
Calculate $\Lambda_m^0$ for $\text{BaCl}_2$ and $\text{Al}_2(\text{SO}_4)_3$ from the following data. For $\Lambda_m^0 \text{ Ba}^{2+} = 127\cdot2\text{ S cm}^2\text{ mol}^{-1}$, $\Lambda_m^0 \text{ Al}^{3+} = 189\text{ S cm}^2\text{ mol}^{-1}$ $\Lambda_m^0 \text{ Cl}^- = 76\cdot3\text{ S cm}^2\text{ mol}^{-1}$, $\Lambda_m^0 \text{ SO}_4^{2-} = 160\text{ S cm}^2\text{ mol}^{-1}$

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2024 · 1 mark · MCQOpen: A potassium iodide ( ) solution containing starch turns blue on the addition of…
A potassium iodide ($\text{KI}$) solution containing starch turns blue on the addition of chlorine. Which one of the following statements explain this? (P) The reduction potential of $\text{Cl}_2$ is more than that of $\text{I}_2$. (Q) The oxidation potential of $\text{Cl}_2$ is more than that of $\text{I}_2$. (R) The product formed when $\text{Cl}_2$ combines with starch is blue. (S) The product formed when $\text{I}_2$ combines with starch is blue.
  • (a)Only P and R
  • (b)Only Q and R
  • (c)Only Q and S
  • (d)Only P and S

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2024 · 5 marks · NumericalOpen: A solution offers the resistance of to a conductivity cell at . If the cell…
Figure for this question
(a)[3.0]
A $0\cdot05\text{ M } \text{NH}_4\text{OH}$ solution offers the resistance of $30\cdot8\text{ ohms}$ to a conductivity cell at $298\text{ K}$. If the cell constant is $0\cdot343\text{ cm}^{-1}$ and molar conductance of $\text{NH}_4\text{OH}$ at infinite dilution is $471\cdot4\text{ S cm}^2\text{mol}^{-1}$, calculate the following: (1) Specific conductance (2) Molar conductance (3) Degree of dissociation
(b)[2.0]
In the diagram of the electrolytic cell given below, A, B and C are connected in series having electrolytes of $\text{ZnSO}_4$, $\text{AgNO}_3$ and $\text{CuSO}_4$ respectively. A steady current of $1\cdot5\text{ A}$ was passed until $1\cdot45\text{ g}$ of $\text{Ag}$ was deposited at the cathode of cell B. (Atomic mass of $\text{Ag} = 108$, $\text{Cu} = 63\cdot5$, $\text{Zn} = 65\cdot3$) Answer the following questions. (1) How long did the current flow? (2) What weight of Cu and Zn was deposited at cathode?

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2023 · 2 marks · NumericalOpen: Calculate the standard free energy change ( ) for the following chemical…
Calculate the standard free energy change ($\Delta G^\circ$) for the following chemical reaction: $\text{Cd}(s) + 2\text{Ag}^+ \longrightarrow \text{Cd}^{2+} + 2\text{Ag}(s)$ Given: $E^\circ_{\text{Cd}^{2+}/\text{Cd}} = -0\cdot40\text{ V}$, $E^\circ_{\text{Ag}^+/\text{Ag}} = +0\cdot80\text{ V}$

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2023 · 5 marks · NumericalOpen: The specific conductance of formic acid is . Calculate its molar conductivity…
(a)[2.5]
The specific conductance of $2\cdot5 \times 10^{-4}\text{ M}$ formic acid is $5\cdot25 \times 10^{-5}\text{ ohm}^{-1}\text{ cm}^{-1}$. Calculate its molar conductivity and degree of dissociation. Given $\lambda^\circ_{\text{H}^+} = 349\cdot5\text{ ohm}^{-1}\text{ cm}^2\text{ mol}^{-1}$ and $\lambda^\circ_{\text{HCOO}^-} = 50\cdot5\text{ ohm}^{-1}\text{ cm}^2\text{ mol}^{-1}$.
(b)[2.5]
Calculate the time taken to deposit $1\cdot27\text{ g}$ of copper at cathode when a current of $2\text{ amp.}$ is passed through the solution of $\text{CuSO}_4$. (Atomic weight of $\text{Cu} = 63\cdot5\text{ g mol}^{-1}$)

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2023 · 5 marks · NumericalOpen: Write the Nernst equation for the cell reaction given below and calculate the…
(i)[3.0]
Write the Nernst equation for the cell reaction given below and calculate the emf of the cell at $298\text{ K}$. $2\text{Cr}(s) + 3\text{Fe}^{2+}(0\cdot1\text{M}) \longrightarrow 2\text{Cr}^{3+}(0\cdot01\text{M}) + 3\text{Fe}(s)$ Given $E^\circ(\text{Cr}^{3+}/\text{Cr}) = -0\cdot74\text{ V}$, $E^\circ(\text{Fe}^{2+}/\text{Fe}) = -0\cdot44\text{ V}$
(ii)[2.0]
Calculate the molar conductance at infinite dilution ($\Lambda^\infty_m$) for $\text{NH}_4\text{OH}$. Given that $\Lambda^\infty_m$ for $\text{Ba(OH)}_2$, $\text{BaCl}_2$ and $\text{NH}_4\text{Cl}$ are $457\text{ ohm}^{-1}\text{cm}^2\text{mol}^{-1}$, $240\text{ ohm}^{-1}\text{cm}^2\text{mol}^{-1}$ and $129\text{ ohm}^{-1}\text{cm}^2\text{mol}^{-1}$ respectively.

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2023 · 5 marks · NumericalOpen: A solution offers a resistance of to a conductivity cell at . If the cell…
(i)[3.0]
A $0\cdot06\text{ molar}$ $\text{CH}_3\text{COOH}$ solution offers a resistance of $55\text{ ohms}$ to a conductivity cell at $25^\circ\text{C}$. If the cell constant is $0\cdot45\text{ cm}^{-1}$ and the molar conductance of $\text{CH}_3\text{COOH}$ at infinite dilution is $398\cdot5\text{ ohm}^{-1}\text{cm}^2\text{mol}^{-1}$. Calculate: (a) Specific conductance (b) Molar conductance (c) Degree of dissociation
(ii)[2.0]
Calculate the number of coulombs of charge required to deposit $24\cdot35\text{ g}$ of aluminium from a solution containing $\text{Al}^{3+}$ ions. (Atomic weight of $\text{Al} = 27$)

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2023 · 2 marks · Short answerOpen: Question
(i)[1.0]

Assertion: Specific conductance of all electrolytes decreases on dilution.

Reason: On dilution, number of ions per unit volume decreases.

  • (a)Both assertion and reason are true and reason is the correct explanation of assertion.
  • (b)Both assertion and reason are true but reason is not the correct explanation for assertion.
  • (c)Assertion is true but reason is false.
  • (d)Assertion is false but reason is true.
(ii)[1.0]

Assertion: Nitration of chlorobenzene leads to the formation of m-nitro chlorobenzene.

Reason: Nitro ($-\text{NO}_2$) group is a m-directing group.

  • (a)Both assertion and reason are true and reason is the correct explanation of assertion.
  • (b)Both assertion and reason are true but reason is not the correct explanation for assertion.
  • (c)Assertion is true but reason is false.
  • (d)Assertion is false but reason is true.

No answer yet.

2023 · 4 marks · Short answerOpen: Select and write the correct alternative from the choices given below: An alkyl…
Select and write the correct alternative from the choices given below:
(i)[1.0]
An alkyl isocyanide on complete reduction gives:
  • (a)Primary amine.
  • (b)Secondary amine.
  • (c)Tertiary amine.
  • (d)Carboxylic acid.
(ii)[1.0]
For a spontaneous reaction $E^\circ_{\text{cell}}$ and $\Delta G^\circ$ will be respectively:
  • (a)-ve and -ve
  • (b)-ve and +ve
  • (c)+ve and -ve
  • (d)+ve and +ve
(iii)[1.0]
Which of the following pairs of transition elements have exceptional electronic configuration?
  • (a)Sc and Cu
  • (b)Fe and Ni
  • (c)Cr and Cu
  • (d)Mn and Zn
(iv)[1.0]
For a first order reaction, when $100\text{ g}$ of the reactant is taken, $75\text{ g}$ of the reactant reacts in 8 minutes. If $200\text{ g}$ of the same reactant is taken, in how much time $150\text{ g}$ of the reactant will react?
  • (a)8 minutes
  • (b)16 minutes
  • (c)20 minutes
  • (d)24 minutes.

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