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Question #44675
The Question
A sample containing moles of a non-stoichiometric iron oxide, \ce{Fe_{0.93}O (s)}, is treated with an aqueous solution containing moles of sodium hypochlorite, \ce{NaClO (aq)}, in a strongly alkaline medium at 298 K. The iron oxide is completely oxidized to soluble ferrate(VI) ions, \ce{FeO4^{2-} (aq)}, while the hypochlorite is reduced to chloride ions, \ce{Cl^- (aq)}. If the redox reaction goes to completion with no excess reagents, what is the exact ratio of ?
Options
- A.
100 : 179
- B.
93 : 179
- C.
1 : 2
- D.
50 : 179
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Mechanism_Trap
Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.
Concepts Behind This Question
Equivalent Concept in Redox|Oxidation State Traps
Why This Question Is Tricky
Common Mistakes
The problem tests the application of the equivalent concept to non-stoichiometric compounds.
The 'Hidden Variable' is the stoichiometric coefficient of the metal in the oxide lattice.
A common student trap is to calculate the change in the average oxidation state of iron (from to , giving a change of ) and incorrectly use this directly as the n-factor, forgetting to multiply by the number of iron atoms per formula unit (0.93).
This leads to the erroneous ratio of .
Another trap is assuming ideal stoichiometry (\ce{FeO}), which yields an n-factor of 4 and a ratio of .
The problem enforces the rule that the n-factor of a compound is the total change in oxidation state for all atoms of the reacting element per mole of the compound.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Some Basic Concepts of Chemistry - Class 11 Part 1 |
| Concept | Equivalent Concept in Redox |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |