Extra Problems for the Web Page for Unit 12: Redox & Electrochemistry.

1. Balance the following reactions in acidic aqueous solution:

a) ClO₃^- + Fe⁺² ---> Cl^- + Fe⁺³ ........................[6Fe⁺²,1ClO₃^-,6H⁺,6Fe⁺³,1Cl^-1,3H₂O]

b) Cr₂O₇^-2 + I₂ ---> Cr⁺³ + IO₃^- .......................[34H⁺, 5Cr₂O₇^-2, 3I₂, 10Cr⁺³, 17H₂O, 6IO₃^-]

2. For the following electrochemical cells, write the oxidation and reduction half-reactions; the overall reaction, and the cell voltage: Use Table N.

a) Co/Co⁺²//Ni⁺²/Ni............................[+0.02 v]

b) Cu/Cu⁺²//Ag⁺/Ag ....................................[+0.46 v]

c) 2Al + 3NiCl₂ ---> 2AlCl₃ + 3Ni ..............[+1.40 v]

3. Using the table of standard reduction potentials, list the following ions in order of decreasing ability as oxidizing agents: F₂ , O₂, Sn⁺⁴, Pb⁺², I₂, Fe⁺³ ........[F₂>Fe⁺³>I₂> Cu⁺²>Sn⁺⁴>Pb⁺²]

4. For the following redox reaction, balance the the equation, using Table N, and predict whether the reaction will proceed spontaneously as written.

Fe⁺² + MnO₄^- + H⁺ -----> Mn⁺² + Fe⁺³ + H₂O .............[5,1,8,1,5,4; spontaneous]

5. If I₂ and Br₂ are added to a solution containing I^- and Br^-, what reaction will occur if the concentration of each species is 1 M. (Use Table N) .......[Br₂ will be reduced to Br^- and I^- will be oxidized to I₂]

6. Will the following redox reaction proceed spontaneously? (Use Table N)

Sn⁺² + Fe⁺³ <----> Sn⁺⁴ + Fe⁺² .............[E⁰ = +0.92 v; spontaneous]

The following problems are for Honors only:

7. Balance the following reaction in basic aqueous solution: (not done in 1998)

SO₃^-2 + CrO₄^-2 -----> SO₄^-2 + Cr(OH)₃ ........[3,2,5H₂O;3,2,4OH^-]

8. Balance the following reaction in aqueous basic solution: (not done in 1998)

MnO₄^- + H₂O₂ -----> MnO₂ + O₂ ...........[2,3,2,3,2H₂O,2OH^-]