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Electrochemistry — NEET & JEE MCQs with answers

NCERT Class 12 · Chemistry · Ch 210 free questions675 in the full bank
Electrochemistry deals with interconversion of chemical and electrical energy. Galvanic cells convert spontaneous redox reactions into electrical work, while electrolytic cells use electrical energy to drive non-spontaneous reactions. Key topics include electrode potentials, the Nernst equation for concentration dependence, conductivity of ionic solutions (Kohlrausch's law), Faraday's laws of electrolysis, batteries, fuel cells, and corrosion.

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Free practice questions

Question 1 · 2.3 Nernst Equation · Easy
Calculate the potential of a hydrogen electrode ($p_{\mathrm{H_2}} = 1$ bar) in contact with a solution whose pH is 10, at 298 K.
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Answer: B — For $\mathrm{H^{+} + e^{-} \rightarrow \tfrac{1}{2}H_2}$ with $E^{\circ} = 0$ and $p_{\mathrm{H_2}} = 1$ bar, the Nernst equation reduces to $E = 0.059\log[\mathrm{H^{+}}] = -0.059\,\mathrm{pH}$. At pH 10 this gives $E = -0.059 \times 10 = -0.59$ V. Option A has the sign reversed, option C ($-0.30$ V) comes from wrongly using $n = 2$, and option D ignores the concentration term.

NCERT Class 12 Chemistry Ch 2 ("Calculate the potential of hydrogen electrode in contact with a solution")

Question 2 · 2.4 Conductance of Electrolytic Solutions · Easy
When the concentration of an electrolytic solution approaches zero, the molar conductivity is known as
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Answer: D — NCERT: "When concentration approaches zero, the molar conductivity is known as limiting molar conductivity and is represented by the symbol $\Lambda_m^{\circ}$."

NCERT Class 12 Chemistry Ch 2 ("conductivity and is represented by the")

Question 3 · 2.8 Corrosion · Easy
Corrosion slowly coats the surfaces of metallic objects with
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Answer: A — NCERT opens the section with 'Corrosion slowly coats the surfaces of metallic objects with oxides or other salts of the metal.'

NCERT Class 12 Chemistry Ch 2 ("Corrosion slowly coats the surfaces of metallic objects with oxides or")

Question 4 · 2.6 Batteries · Easy
The anode of the mercury cell is
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Answer: D — NCERT: the mercury cell 'consists of zinc - mercury amalgam as anode'.

NCERT Class 12 Chemistry Ch 2 ("like hearing aids, watches, etc. consists of zinc - mercury")

Question 5 · 2.2 Galvanic Cells · Medium
The cell potential is the difference between the electrode potentials of the cathode and the anode. In this statement the two electrode potentials must both be taken as:
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Answer: A — NCERT puts the qualifier in brackets: the cell potential is the difference between the electrode potentials (reduction potentials) of the cathode and anode. Both values are therefore reduction potentials, which is why $E_{cell} = E_{cathode} - E_{anode}$ works only when the anode value is not first converted into an oxidation potential.

NCERT Class 12 Chemistry Ch 2 ("the difference between the electrode potentials")

Question 6 · 2.5 Electrolytic Cells and Electrolysis · Hard
The chemical equivalent weights of Ag (atomic mass 108, Ag$^{+}$), Cu (atomic mass 63, Cu$^{2+}$) and Al (atomic mass 27, Al$^{3+}$) are respectively
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Answer: C — Equivalent weight = atomic mass $\div$ number of electrons needed to reduce the cation: $108/1=108$ for Ag, $63/2=31.5$ for Cu and $27/3=9$ for Al.

NCERT Class 12 Chemistry Ch 2 ("of Metal ÷ Number of electrons required to reduce the cation).")

Question 7 · 2.7 Fuel Cells · Medium
Fuel cells have so far been used in automobiles
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Answer: A — NCERT: 'These have been used in automobiles on an experimental basis.'

NCERT Class 12 Chemistry Ch 2 ("These have been used in automobiles on an experimental basis. Fuel")

Question 8 · 2.1 Electrochemical Cells · Medium
The footnote attached to the statement about unit ion concentrations warns that, strictly speaking, which quantity should be used in place of concentration?
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Answer: C — The footnote reads that strictly speaking activity should be used instead of concentration. Activity is the rigorous quantity; concentration is used in the elementary treatment as a working substitute. Molality, mole fraction and partial pressure are not the quantity named in that footnote.

NCERT Class 12 Chemistry Ch 2 ("Strictly speaking activity should be used instead of concentration")

Question 9 · 2.3 Nernst Equation · Medium
When the natural logarithm in Eq. (2.11) is converted to base $10$ and the values of $R$, $F$ and $T = 298$ K are substituted, the factor $\dfrac{2.303RT}{F}$ takes the value
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Answer: C — Substituting $R = 8.314$ J K$^{-1}$ mol$^{-1}$, $T = 298$ K and $F = 96487$ C mol$^{-1}$ gives $\dfrac{2.303 \times 8.314 \times 298}{96487} = 0.059$ V, which is why Eq. 2.12 carries the coefficient $\dfrac{0.059}{n}$. Omitting the factor $2.303$ leaves $\dfrac{RT}{F} = 0.0257$ V, dividing further by $n = 2$ gives $0.0295$ V, and doubling gives $0.118$ V.

NCERT Class 12 Chemistry Ch 2 ("By converting the natural logarithm in Eq. (2.11) to the base 10 and")

Question 10 · 2.4 Conductance of Electrolytic Solutions · Hard
A conductivity cell of cell constant $2.5$ cm$^{-1}$ contains a solution of conductivity $2.5\times10^{-3}$ S cm$^{-1}$. The conductance of the solution in that cell is
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Answer: B — From $\kappa=G^{*}/R$ and $G=1/R$, we get $G=\dfrac{\kappa}{G^{*}}=\dfrac{2.5\times10^{-3}}{2.5}=1\times10^{-3}$ S.

NCERT Class 12 Chemistry Ch 2 ("Cell constant = G* = conductivity × resistance")

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