Answer all assigned questions and problems, and show all work.
- Balance the following redox equations by the ion-electron method.
(25 points)
- H2O2 + Fe+2 → Fe+3 + H2O (in acidic solution)
- Cu + HNO3 → Cu+2 + NO + H2O (in acidic solution)
- CN– + MnO4– → CNO– + MnO2 (in basic solution)
- Br2 → BrO3– + Br– (in basic solution)
- S2O3–2 + I2 → I– + S4O62– (in acidic solution)
- Calculate the standard emf of a cell that uses the Mg/Mg+2 and Cu/Cu+2 half-cell reactions at 25ºC. Write the equation for the cell reaction that occurs under standard-state conditions. (10 points)
- Predict whether Fe+3 can oxidize I– to I2 under standard-state conditions. (10 points)
- Consider the following half-reactions:
MnO4–(aq) + 8H+(aq) + 5e– → Mn+2(aq) + 4H2O(l)
NO3–(aq) + 4H+(aq) + 3e– → NO(g) + 2H2O(l)
Predict whether NO3– ions will oxidize Mn+2 to MnO4– under standard state conditions. (8 points)
- Which species in each pair is a better oxidizing agent under standard-state conditions? (16 points)
- Br2 or Au3+
- H2 or Ag+
- Cd2+ or Cr3+
- O2 in acidic media or O2 in basic media
- Under standard-state conditions, what spontaneous reaction will occur in aqueous solution among the ions Ce4+, Ce3+, Fe3+, and Fe2+? Calculate ∆Go and K for this reaction. (8 points)
- What is the potential of a cell made up of Zn/Zn2+ and Cu/Cu2+ half-cells at 25ºC if [Zn2+] = 0.25 M and [Cu2+] = 0.15 M? (8 points)
- Consider the electrolysis of molten barium chloride, BaCl2. (a) Write the half-reactions. (b) How many grams of barium metal can be produced by supplying 0.50 A for 30 minutes? (10 points)
- In a certain electrolysis experiment involving Al3+ ions, 60.2 g of Al is recovered when a current of 0.352 A is used. How many minutes did the electrolysis last? (5 points)
