Question

Which species in each pair is a better oxidizing agent under standard-state conditions? (a) br2 au3+ (b) h2 ag+ (c) cd2+ cr3+ (d) o2 in acidic media o2 in basic media?

Answer 1

Answer:

(a) Au³⁺;  (b) Ag⁺; (c) Cd²⁺; (d) O₂ in acidic media

Explanation:

You've had Trends in the Periodic Table. Now, here are Trends in Standard Reduction Potentials.

• The strength of oxidizing agents increases from bottom to top on the left-hand side.
• The strength of reducing agents increases from top to bottom on the right-hand side.

Thus, for each pair of half reactions, we need to look only at which one has the more positive standard reduction potential.

(a) Br₂/Au³⁺  

Au³⁺(aq) + 3e⁻ ⟶ Au(s)       1.498 V

Br₂(ℓ) + 2e⁻ ⟶ 2Br⁻(aq)      1.066 V

Au³⁺ is the stronger oxidizing agent.

(b) H₂/Ag⁺  

Ag⁺(aq) + e⁻ ⟶ Au(s)          0.7996 V

H₂(g) + 2e⁻ ⟶ 2H⁻(aq)      -2.33      V

Ag⁺ is the stronger oxidizing agent.

(c) Cd²⁺/Cr³⁺  

Cd²⁺(aq) + e⁻ ⟶ Cd(s)      -0.4030 V

Cr³⁺(aq) + 3e⁻ ⟶ Cr(s)      -0.744   V

Cd²⁺ is the stronger oxidizing agent.

(d) O₂, H⁺/O₂, OH⁻  

O₂(g) + 4H⁺(aq) + 4e⁻ ⟶ 2H₂O(ℓ)         1.224 V

O₂(g) + H₂O(ℓ) + 4e⁻ ⟶ 4OH⁻(aq)       0.401  V

O₂ in acid is the stronger oxidizing agent.