COMEDK2025Chemistryd and f Block ElementsActual
Two statements, one Assertion and the other Reason, are given. Choose the right option. Assertion: The Standard Electrode potential, E ^0 Co ³⁺ / Co ²⁺ is greater than E ^0 Fe ³⁺ / Fe ²⁺ . Reason: Co ³⁺ ions are less stable in aqueous medium than Fe ³⁺ ions which has stable d ^5 configuration
Options
- AAssertion is correct but Reason is incorrect.
- BBoth Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
- CBoth Assertion and Reason are correct and Reason is the correct explanation of Assertion.
- DAssertion is incorrect but Reason is correct.
Correct answer
C. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Step-by-step solution
The standard electrode potential E⁰ for the reduction M³⁺ + e⁻ M²⁺ depends on the stability of the M³⁺ and M²⁺ oxidation states in aqueous solution. For iron, the Fe³⁺ ion has a stable d⁵ configuration, making it relatively stable compared to Fe²⁺ ( d⁶ ), resulting in a lower reduction potential of +0.77 V. For cobalt, the Co³⁺ ion has a d⁶ configuration and is a strong oxidizing agent because it is highly unstable in aqueous medium compared to Co²⁺ ( d⁷ ), which is more stable. Consequently, the reduction potentia