III. Questions 1. Analyze the oxidation-reduction process used in this experimen
ID: 1045497 • Letter: I
Question
III. Questions 1. Analyze the oxidation-reduction process used in this experiment. Include oxidation numbers, half-reactions, and complete balanced reactions. 2. Analyze the same oxidation-reduction process as if it were in a basic solution. 3. Comment on the need for a blank when doing a permanganate standardization. 4. Analyze the oxidation-reduction process that occurs when hydrogen peroxide I decomposes. 5. The concentration of a hydrogen peroxide solution is sometimes expressed as "volume percent," which here means the number of 100 mL volumes of oxygen gas (under standard temperature and pressure, STP) liberated from 100 mL of the given solution upon complete decomposition of hydrogen peroxide into water and oxygen. Calculate the volume percent of peroxide in your unknown, how does it compare to the volume listed on the bottle? If you don't remember what STP is, please look it up.Explanation / Answer
1. In strongly acidic medium, MnO4- undergoes a five electron reduction to colorless manganous, Mn(II), ion:
MnO4-+ 8 H+ + 5 e- ? Mn2+ + 4 H2O
Potassium permanganate is not pure enough to be used as a primary standard. In addition, the oxidizing power of MnO4- is sufficiently great to oxidize water as follows: 4 MnO4- + 2 H2O ? 4 MnO2 (s) + 4 OH- + 3 O2 (g)
Reaction taking place during titration is
2MnO4- + 5H2O2 + 6H+ ? 2Mn2+ + 5O2 + 8H2O
Hydrogen peroxide is usually treated as a strong oxidizer, but in the presence of even stronger oxidizer it can become a reducing agent:
H2O2 ? O2 + 2H+ + 2e-