Oxidation-Reduction

The following problems are taken from T. L. Brown, H. E. Lemay, B. E. Bursten, & J. R. Burdge, Chemistry: The Central Science, Ninth Edition, Chapter 20.

  4)  Indicate whether the following balanced equations involve oxidation-reduction. If they do, identify the elements that undergo changes in oxidation number.

       (a) PBr₃(l) + 3H₂O(l) H₃PO₃(aq) + 3HBr(aq)

       (b) NaI(aq) + 3HOCl(aq) NaIO₃(aq) + 3HCl(aq)

       (c) 3SO₂(g) + 2HNO₃(aq) + 2H₂O(l) 3H₂SO₄(aq) + 2NO(g)

       (d) 2H₂SO₄(aq) + 2NaBr(s) Br₂(l) + SO₂(g) + Na₂SO₄(aq) + 2H₂O(l)

  6) Hydrazine (N₂H₄) and dinitrogen tetroxide (N₂O₄) form a self-igniting mixture that has been used as a rocket propellant. The reaction products are N₂ and H₂O.

      (a) Write a balanced chemical equation for this reaction.

      (b) Which substance serves as the reducing agent, and which as the oxidizing agent?

10) Complete and balance the following equations, and identify the oxidizing and reducing agents.

      (b) As(s) + ClO₃^-(aq) H₃AsO₃(aq) + HClO(aq) (acidic solution)

      (f) H₂O₂(aq) + Cl₂O₇(aq) ClO₂^-(aq) + O₂(g) (basic solution)

34) From each of the following pairs of substances, choose the one that is the stronger reducing agent:      

      (a) Fe(s) or Mg(s)       

      (b) Ca(s) or Al(s)

      (c) H₂(g, acidic solution) or H₂S(g)

      (d) H₂SO₃(aq) or H₂C₂O₄(aq)

38) (a) Which of the following is the strongest oxidizing agent, and which is the weakest in acidic solution: Ce⁴⁺, Br₂, H₂O₂, Zn?

      (b) Which of the following is the strongest reducing agent, and which is the weakest in acidic solution: F^-, Zn, N₂H₅⁺, I₂, NO?