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Question #44272

Difficulty: 8/10 | 🟢 Free

The Question

Element $M$ is a 3d-block transition metal. In its ground state, the subshell with the highest $(n+l)$ value contains exactly 5 electrons, and the subshell with the highest principal quantum number ( $n$ ) contains exactly 1 electron. An aqueous solution of $\ce{K2M2O7}$ has a molality of $0.20 \text{ mol kg}^{-1}$ and a density of $1.3235 \text{ g mL}^{-1}$ . Calculate the volume of this $\ce{K2M2O7}$ solution required to completely oxidize a mixture containing $0.10 \text{ moles}$ of $\ce{FeC2O4}$ and $0.05 \text{ moles}$ of $\ce{Fe2(C2O4)3}$ in an acidic medium. (Given molar masses in $\text{g mol}^{-1}$ : $K = 39$ , $O = 16$ , $M = 52$ )

Options

A.
400 mL
B.
500 mL
C.
800 mL
D.
200 mL

Check Your Answer

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

Energy of Subshells (n+l rule)|Concentration Unit Interconversion|Dimensional Consistency of Constants

Why This Question Is Tricky

Common Mistakes

This problem tests three distinct conceptual traps.

First, it requires identifying Chromium via its anomalous $(n+l)$ electronic configuration ( $3d^5 4s^1$ ).

Second, it forces a rigorous Molality-to-Molarity conversion; students who lazily approximate Molarity ≈ Molality (ignoring the high density of 1.3235 g/mL) will incorrectly calculate 500 mL (Option B).

Third, it tests redox stoichiometry of mixed salts: a common trap is assuming Ferric Oxalate (Fe2(C2O4)3) does not react because Fe is already in the +3 state, forgetting that the oxalate anion is still a potent reducing agent (leading to Option D).

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Structure of Atom - Class 11 Part 1
Concept	Energy of Subshells (n+l rule)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free