ISC Chemistry 2026 Board Exam Practice Papers -ELECTROCHEMISTRY

  ISC - Class 12  

CHEMISTRY – TEST

ELECTROCHEMISTRY

(THEORY) (50 min.)

Question 1
[A] Choose the most appropriate word to complete the following statement.                                 [3]
[Displaces, low, high, one, half, negative, positive]
(i)    Copper ____________ silver from its solution because it has a __________ reduction potential.
(ii)   For a spontaneous reaction, free energy change is ___________.
(iii)  The number of gram atom of copper deposited from a solution of CuSO₄ by 1 F is __________.

[B] Choose the correct alternative.                                                                                                      [4]
(i).   When a copper wire is dipped into a silver nitrate solution, silver is precipitated because:
(a) Both Ag & Cu have the reduction potential (R.Р.)                      (b) R.Р of Ag is higher than that of Cu.
(c) R.Р. of Cu is higher than that of Ag.                                           (d) Both Ag &Cu have negative R.Р.
(ii).  The unit of conductance is ___.
(a) Mho                                (b) Ohm–1                                              (c) Siemens                            (d)  All of the above
(iii). For a redox reaction to be feasible, EMF of the cell should be ___.
(a) Negative                          (b)  zero                                  (c) positive                                    (d) non-zero
(iv). Assertion: The Daniell cell stops working when both solutions attain the same ionic concentration.
Reason: The electrode potentials of the two half-cells become equal.
Reason: The electrode potentials of the two half-cells become equal.
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 of Assertion.
C. Assertion is true, but Reason is false.
D. Assertion is false, but Reason is true.

[C] A Daniell cell consists of a zinc electrode placed in ZnSO₄ solution and a copper electrode placed in CuSO₄ solution. The two half-cells are connected by a salt bridge and an external circuit. Zinc loses electrons while copper ions gain electrons.
Answer the following:
(i).   Identify the anode and cathode.                                                                                                       (1)
(ii).  Write the half-reaction occurring at the anode.                                                                               (1)
(iii).  What is the function of the salt bridge?                                                                                         (1)                                                                             
Question 2: How many faradays of electricity are required to liberate 3 moles of hydrogen gas in the electrolysis of an aqueous solution?                                                                                                         [2]
Question 3: State and explain the Kohlrausch law.                                                                                 [2]
Question 4: Why is the equilibrium constant K related only to E^o cell and not to E cell ?                    [2]
Question 5: Calculate the maximum possible electrical work that can be obtained from the cell constructed by connecting a silver half- cell with a copper half-cell under standard conditions.
Given: E^o Cu²⁺/Cu = +0.34 V;  E^o Ag⁺/Ag = +0.80 V                                                                           [3]
Question 6: Calculate the cell potential of the given cell at 25 °C (R = 8.31 J K^–1 mol^–1, F = 96500 C mol^–1)

            Ni | Ni²⁺ (0.01 M) || Cu²⁺ (0.1 M) | Cu       

       Given: E^o_Cu²⁺_|Cu = 0.34 V, E^o_Ni²⁺_|Ni = – 0.25 V  
    
Question 7: Calculate molar conductivity (Λo) for NH4OH, given that values of Λo for Ba(OH)2, BaCl2, and NH4Cl are 523.3, 280.0, and 130.0 S cm2 mol-1, respectively.                                           [3]
Question 8:                                                                                                                                               [5]
(a)   Calculate the equilibrium constant for the reaction                                                       
(b)   Calculate the potential of the following cell reaction at 298 K.
The standard potential (Eº) of the cell is 0.89 V. Will the potential of the cell increase or decrease if the concentration of Sn4+ is increased in the cell? (R = 8.314 kJ^–1mol^–1,F = 96500 C mol^–1)
OR
(a)   Represent the cell in which the following reaction takes place
   Mg(s) + 2Ag⁺(0.0001M) → Mg²⁺(0.130M) +2Ag(s)         Calculate its E_(cell)  if E _(cell)° = 3.17 V                                                                                                                  

(b)   Find the Gibbs energy change of the cell at 298K.       Cr |Cr³⁺ (0.1M) || Cu²⁺(0.01M) |Cu
              Given E° Cr³⁺ / Cr = – 0.75V, Cu²⁺/Cu = + 0.34V, F = 96500C.