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Question #44681

Difficulty: 8/10 | 🟢 Free

The Question

A metal MM (Atomic mass = 115 g mol−1115 \text{ g mol}^{-1}) forms two chlorides, AA and BB. Elemental analysis reveals that 1.00 g1.00 \text{ g} of MM combines with 0.308 g0.308 \text{ g} of chlorine in compound AA, and with 0.924 g0.924 \text{ g} of chlorine in compound BB.

0.30 moles0.30 \text{ moles} of solid AA is dissolved in 1 L1 \text{ L} of water at 298 K298 \text{ K}. Upon dissolution, the metal ion undergoes complete disproportionation into solid metal MM and the higher oxidation state metal ion found in BB.

The resulting aqueous mixture is filtered, and the filtrate is electrolyzed using a current of 9.65 A9.65 \text{ A} for 1000 s1000 \text{ s}. Due to concurrent H2H_2 gas evolution at the cathode, the current efficiency for the deposition of MM is only 60%60\%.

Calculate the total mass of solid metal MM recovered from both the initial dissolution process and the subsequent electrolysis. (Given: F=96500 C mol−1F = 96500 \text{ C mol}^{-1}, Atomic mass of Cl=35.5 g mol−1Cl = 35.5 \text{ g mol}^{-1})

Options

  • A.

    25.3 g

  • B.

    6.9 g

  • C.

    26.8 g

  • D.

    2.3 g

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

Law of Multiple Proportions|Equivalent Concept in Redox|Electrolysis Product Prediction

Why This Question Is Tricky

Common Mistakes

This problem tests the intersection of stoichiometry (Law of Multiple Proportions) and electrochemistry, specifically targeting the assumption that metal ions remain stable in aqueous solutions.

The 'Hidden Variable' is the disproportionation of the +1 oxidation state (common for Group 13 metals like Indium) before electrolysis even begins.

Students who blindly apply Faraday's laws to the initial 0.30 moles of M+ will fall into the trap of calculating deposition based on a 1-electron reduction, completely missing the 23.0 g of metal precipitated chemically and the altered n-factor (3) for the remaining ions.

Furthermore, the non-ideal current efficiency (60%) due to concurrent H2 evolution acts as a secondary kinetic trap, punishing those who assume 100% Faradaic yield.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterSome Basic Concepts of Chemistry - Class 11 Part 1
ConceptLaw of Multiple Proportions
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree