JEE Main Electrochemistry Previous Year Questions (2002–2026)

5 real JEE Main questions on Redox & Electrochemistry, straight from past papers. Try them, then check the answer.

1. Q1JEE Main 2026 (Online) 28th January Evening Shift

   A volume of x mL of 5 M NaHCO₃ solution was mixed with 10 mL of 2 M H₂CO₃ solution to make an electrolytic buffer. If the same buffer was used in the following electrochemical cell to record a cell potential of 235.3 mV, then the value of x = ______ mL (nearest integer).

   Sn(s) | Sn(OH)₆²⁻ (0.5 M) | HSnO₂⁻ (0.05 M) | OH⁻ | Bi₂O₃(s) | Bi(s)

   Consider up to one place of decimal for intermediate calculations

   
   $\left[\begin{array}{ll}\text { Given: } & E_{Sn\left( {OH} \right)_6^{2 - } |HSnO_2^ -}^o = - 0.9V \ & \mathrm{E}^{\mathrm{o}}{ }_{\mathrm{Bi}_2 \mathrm{O}_3 \mid \mathrm{Bi}}=-0.44 \mathrm{~V} \ & \mathrm{pKa}_{\left(\mathrm{H}_2 \mathrm{CO}_3\right)}=6.11 \ & \frac{2.303 \mathrm{RT}}{\mathrm{F}}=0.059 \mathrm{~V} \ & \text { Antilog }(1.29)=19.5\end{array}\right]$
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2. Q2JEE Main 2025 (Online) 29th January Morning Shift

   For a Mg | Mg²⁺ (aq) || Ag⁺ (aq) | Ag the correct Nernst Equation is :

   1. A
      $\mathrm{E}_{\text {cell }}$​${}=\mathrm{E}_{\text {cell }}^{\mathrm{o}}-\frac{\mathrm{RT}}{2 \mathrm{~F}} \ln \frac{\left[\mathrm{Ag}^{+}\right]^2}{\left[\mathrm{Mg}^{2+}\right]}$
   2. B
      $\mathrm{E}_{\text {cell }}$​${}=\mathrm{E}_{\text {cell }}^{\mathrm{o}}-\frac{\mathrm{RT}}{2 \mathrm{~F}} \ln \frac{\left[\mathrm{Mg}^{2+}\right]}{\left[\mathrm{Ag}^{+}\right]}$
   3. C
      $\mathrm{E}_{\text {cell }}$​${}=\mathrm{E}_{\text {cell }}^{\mathrm{o}}-\frac{\mathrm{RT}}{2 \mathrm{~F}} \ln \frac{\left[\mathrm{Ag}^{+}\right]}{\left[\mathrm{Mg}^{2+}\right]}$
   4. D
      $\mathrm{E}_{\text {cell }}$​${}=\mathrm{E}_{\text {cell }}^{\mathrm{o}}+\frac{\mathrm{RT}}{2 \mathrm{~F}} \ln \frac{\left[\mathrm{Ag}^{+}\right]^2}{\left[\mathrm{Mg}^{2+}\right]}$
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3. Q3JEE Main 2024 (Online) 5th April Evening Shift

   For the electro chemical cell

   $\mathrm{M}\left|\mathrm{M}^{2+}\right||\mathrm{X}| \mathrm{X}^{2-}$

   If $\mathrm{E}_{\left(\mathrm{M}^{2+} / \mathrm{M}\right)}^0$​${}=0.46 \mathrm{~V}$ and $\mathrm{E}_{\left(\mathrm{x} / \mathrm{x}^{2-}\right)}^0$​${}=0.34 \mathrm{~V}$.

   Which of the following is correct?

   1. A
      $\mathrm{E}_{\mathrm{cell}}$​${}=0.80 \mathrm{~V}$
   2. B
      $\mathrm{M}+\mathrm{X} \rightarrow \mathrm{M}^{2+}+\mathrm{X}^{2-}$ is a spontaneous reaction
   3. C
      $\mathrm{E}_{\text {cell }}$​${}=-0.80 \mathrm{~V}$
   4. D
      $\mathrm{M}^{2+}+\mathrm{X}^{2-} \rightarrow \mathrm{M}+\mathrm{X}$ is a spontaneous reaction
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4. Q4JEE Main 2023 (Online) 1st February Evening Shift

   Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R)

   Assertion (A) : An aqueous solution of KOH when used for volumetric analysis, its concentration should be checked before the use.

   Reason (R) : On aging, KOH solution absorbs atmospheric $\mathrm{CO}_{2}$.

   In the light of the above statements, choose the correct answer from the options given below :

   1. A
      (A) is correct but (R) is not correct
   2. B
      (A) is not correct but (R) is correct
   3. C
      Both (A) and (R) are correct but (R) is not the correct explanation of (A)
   4. D
      Both (A) and (R) are correct and (R) is the correct explanation of (A)
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5. Q5JEE Main 2022 (Online) 25th June Morning Shift

   In a cell, the following reactions take place

   $$\begin{array}{ccc} {F{e^{2 + }} \to F{e^{3 + }} + {e^ - }} & {E_{F{e^{3 + }}/F{e^{2 + }}}^o = 0.77\,V} \\ {2{I^ - } \to {I_2} + 2{e^ - }} & {E_{{I_2}/{I^ - }}^o = 0.54\,V} \end{array} $$

   The standard electrode potential for the spontaneous reaction in the cell is x $\times$ 10^$-$2 V 298 K. The value of x is ____________. (Nearest Integer)

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