Answer to Question #286484 in Chemistry for khryst

Question

1.     Which of the following reaction is a reduction reaction?

a.      Fe → Fe³⁺

b.     Cr → Cr³⁺

c.      MnO₄^2– → MnO₄^–

d.     Na⁺ → Na

 

2.     Which of the following reaction is a reduction reaction?

a.      Fe²⁺ → Fe³⁺

b.     Sn²⁺ → Sn⁴⁺

c.      Fe(CN)₆^3– → Fe(CN)₆^4–

d.     Mn²⁺ → MnO₄^–

Answer 1

Solution:

(1) Which of the following reaction is a reduction reaction?

a) Fe − 3e⁻ → Fe³⁺ (oxidation half-reaction)

b) Cr − 3e⁻ → Cr³⁺ (oxidation half-reaction)

c) 3MnO₄^2– + 4H⁺ → 2MnO₄^– + MnO₂ + 2H₂O (disproportionation reaction, self-redox)

d) Na⁺ + e⁻ → Na (reduction half-reaction)

Answer (1):

d) Na⁺ → Na

(2) Which of the following reaction is a reduction reaction?

a) Fe²⁺ − e⁻ → Fe³⁺ (oxidation half-reaction)

b) Sn²⁺ − 2e⁻→ Sn⁴⁺ (oxidation half-reaction)

c) Fe(CN)₆^3– + e⁻ → Fe(CN)₆^4– (reduction half-reaction)

d) Mn²⁺ + 8OH^– − 5e⁻→ MnO₄^– + 4H₂O (oxidation half-reaction)

Answer (2):

c) Fe(CN)₆^3– → Fe(CN)₆^4–