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. To see the solution to a problem or to return from the solution, click on the number of the problem.


  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?        

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