Question

For which of the following electrode reactions the standard electrode potential is the highest at 298 K? The ions are present in aqueous solution. ________.

• A. $Co^{3+}+e^{-}\rightarrow Co^{2+}$
• B. $Cl_{2(g)}+2e^{-}\rightarrow2Cl^{-}$
• C. $MnO_{2(s)}+4H^{+}+2e^{-}\rightarrow Mn^{2+}+2H_{2}O$
• D. $F_{2(g)}+2e^{-}\rightarrow2F^{-}$
• E. $AgCl_{(s)}+e^{-}\rightarrow Ag_{(s)}+Cl^{-}$

Hint:

Fluorine is at the very top of the electrochemical series with the highest reduction potential.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
The standard electrode potential (\(E^{\circ}\)) is a measure of a species' tendency to be reduced. A higher (more positive) \(E^{\circ}\) value indicates a stronger tendency to gain electrons and act as an oxidizing agent. The question asks to identify the reaction with the highest \(E^{\circ}\), which is equivalent to identifying the strongest oxidizing agent in the list.
Step 2: Key Formula or Approach
This is a knowledge-based question that relies on understanding the electrochemical series and periodic trends. The strength of an oxidizing agent is related to its electronegativity. The most electronegative element will have the greatest desire to accept electrons, making it the strongest oxidizing agent and giving it the highest standard reduction potential.
Step 3: Detailed Explanation
Let's analyze the species being reduced in each reaction:
(A) \(Co^{3+}\): A high oxidation state metal ion, a strong oxidizing agent. (\(E^\circ \approx +1.82 \text{ V}\)) (B) \(Cl_2\): A halogen, known to be a good oxidizing agent. (\(E^\circ = +1.36 \text{ V}\)) (C) \(MnO_2\) (in acid): Manganese in a +4 oxidation state, a good oxidizing agent. (\(E^\circ \approx +1.23 \text{ V}\)) (D) \(F_2\): Fluorine is the most electronegative element in the periodic table. It has an extremely strong tendency to accept electrons to form the stable fluoride ion (\(F^-\)). This makes gaseous fluorine the strongest known chemical oxidizing agent. Its standard reduction potential is the highest among all elements. (\(E^\circ = +2.87 \text{ V}\)) (E) \(AgCl\): A sparingly soluble salt being reduced. (\(E^\circ = +0.22 \text{ V}\)) Comparing these, Fluorine (\(F_2\)) is by far the strongest oxidizing agent. Therefore, its reduction half-reaction will have the highest standard electrode potential.
Step 4: Final Answer
The reaction \(F_2(g) + 2e^- \to 2F^-\) has the highest standard electrode potential.