The decreasing order of standard electrode potential of Mg, K, Ba and Ca, is — Electrochemistry Chemistry Question

💡 Solution & Explanation

Step 1 - Conceptual Understanding By IUPAC convention, standard electrode potential means standard reduction potential. A more positive (less negative) value means the metal is less reactive. Step 2 - Analyzing the Given Standard Reduction Potential Values At $298\text{ K}$: * $E^\circ(\ce{Mg^{2+}/Mg}) = -2.37\text{ V}$ * $E^\circ(\ce{Ca^{2+}/Ca}) = -2.87\text{ V}$ * $E^\circ(\ce{Ba^{2+}/Ba}) = -2.90\text{ V}$ * $E^\circ(\ce{K^{+}/K}) = -2.93\text{ V}$ Step 3 - Determining the Decreasing Order Ordering from highest (least negative) to lowest (most negative): $$-2.37\text{ V} > -2.87\text{ V} > -2.90\text{ V} > -2.93\text{ V}$$ $$\text{Decreasing order: } \ce{Mg > Ca > Ba > K}$$ Step 4 - Evaluation of Options * **Option (A)** $\text{K, Ca, Ba, Mg}$ — incorrect (K has the lowest potential). * **Option (B)** $\text{Ba, Ca, K, Mg}$ — incorrect. * **Option (C)** $\text{Ca, Mg, K, Ba}$ — incorrect (Mg has higher potential than Ca). * **Option (D)** $\text{Mg, Ca, Ba, K}$ — correct. $$\text{Correct Option: } \boxed{\text{D}}$$