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.
[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 Eo
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: Eo Cu2+/Cu = +0.34 V; Eo
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: EoCu2+|Cu
= 0.34 V, EoNi2+|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
= 0.34 V, EoNi2+|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.
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