Question

Consider the following reduction potentials:

2H+ + 2e– → H2 E° = 0.00 V Ni2+ + 2e– → Ni E° = -0.25 V Cd2+ + 2e– → Cd E° = -0.40 V
Based on this information which pairs of substances will react spontaneously under standard state conditions?

Answer 1

H⁺/H₂//Ni/Ni⁺²; H⁺/H₂//Cd/Cd⁺²; Ni⁺²/Ni//Cd/Cd⁺²

Step-by-step explanation:

The redox reactions are spontaneously when the E° of the substance that is reduced is higher than the E° of the substance that is oxidized. The substance is reduced when gaining electrons and is oxidized when loses electrons.

So, the reactions that occur spontaneously are:

2H⁺ + Ni → H₂ + Ni⁺² (H⁺ is reduced and Ni is oxidized)

2H⁺ + Cd → H₂ + Cd⁺² (H⁺ is reduced and Cd is oxidized)

Ni⁺² + Cd → Ni + Cd⁺² (Ni⁺² is reduced and Cd is oxidized)

Pairs: H⁺/H₂//Ni/Ni⁺²; H⁺/H₂//Cd/Cd⁺²; Ni⁺²/Ni//Cd/Cd⁺²