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Question #44732

Difficulty: 8/10 | 🟢 Free

The Question

A galvanic cell is constructed at 298 K298\text{ K} using Zirconium and Hafnium electrodes immersed in their respective hydroxide suspensions:

\ceZr(s)∣Zr(OH)4(s)∣Buffer(pH=2.0)∣∣Buffer(pH=1.5)∣Hf(OH)4(s)∣Hf(s)\ce{Zr(s) | Zr(OH)4(s) | Buffer (pH = 2.0) || Buffer (pH = 1.5) | Hf(OH)4(s) | Hf(s)}

Due to the lanthanoid contraction, \ceZr\ce{Zr} and \ceHf\ce{Hf} exhibit nearly identical atomic/ionic radii and chemical properties. Consequently, assume their standard reduction potentials are equal (E\ceZr4+/Zr∘=E\ceHf4+/Hf∘E^\circ_{\ce{Zr^{4+}/Zr}} = E^\circ_{\ce{Hf^{4+}/Hf}}) and their hydroxide solubility products are identical (Ksp=10−52K_{sp} = 10^{-52}). Assuming \ceM4+\ce{M^{4+}} is the only soluble metal species, calculate the cell potential (EcellE_{cell}) at 298 K298\text{ K}.

(Given: 2.303RTF=0.059 V\frac{2.303 RT}{F} = 0.059\text{ V})

Options

  • A.

    +0.0295 V+0.0295\text{ V}

  • B.

    −0.0295 V-0.0295\text{ V}

  • C.

    +0.118 V+0.118\text{ V}

  • D.

    +0.0590 V+0.0590\text{ V}

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Nernst Equation Concentration Dependence|Post-Lanthanoid Radii Equality|Lanthanoid Contraction cause

Why This Question Is Tricky

Common Mistakes

This problem tests the intersection of Periodic Trends (Lanthanoid Contraction) and Electrochemistry.

Students often panic when presented with two different metals without explicit E∘E^\circ values.

The 'Hidden Variable' is recognizing that the Lanthanoid Contraction equalizes the standard reduction potentials and solubility products of Zr and Hf, effectively reducing the system to a concentration cell (Ecell∘=0E^\circ_{cell} = 0).

Furthermore, it traps students who fail to correctly apply the 4th power dependence of the hydroxide concentration in the KspK_{sp} expression or who mistakenly use [\ceH+][\ce{H+}] instead of [\ceOH−][\ce{OH-}] to find the reaction quotient QQ.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterElectrochemistry - Class 12
ConceptNernst Equation Concentration Dependence
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree