Redox Titrations

MnO₄^- + 5Fe²⁺ + 8H⁺ --> Mn²⁺ + 4H₂O + 5Fe³⁺

What volume of 0.01M MnO₄^- reacts with 0.002 moles of Fe²⁺?

• 0.1 dm³

• 0.04 dm³

• 0.4 dm³

• 1.0 dm³

2MnO₄^- + 6H⁺ + 5H₂O₂ --> 2Mn²⁺ + 8H₂O + 5O₂

What volume of 0.1M H₂O₂ react with 0.004 moles of MnO₄^-?

• 0.1 dm³

• 0.2 dm³

• 0.04 dm³

• 1.00 dm³

Explain the meaning of Biological Oxygen Demand or BOD.

• the amount of oxygen used to decompose the organic matter in a sample of water over 5 days time.

• the amount of oxygen produced in a sample of water over 5 days time.

• the amount of oxygen used to synthesize the organic matter in a sample of water over 5 days time.

• the amount of oxygen released from a sample of water over 5 days time.

Given the equations for the Winkler method:

1. 2Mn²⁺ + O₂ + 4OH^- → 2MnO₂ + 2H₂O

2. MnO₂ + 2I^- + 4H⁺ → Mn²⁺ + I₂ + 2H₂O

3. 2S₂O₃^2- + I₂ → 2I^- + S₄O₆^2-

If 0.500 moles of S₂O₃^2- are consumed in the titration, find the number of moles of O₂ in the water sample.

• 2.00 mol

• 0.250 mol

• 0.125 mol

• 1.00 mol

A sample of water is analyzed by the Winkler method to find that its water Oxygen concentration is 0.0002 mol dm^-3. Find the concentration in ppm.

• 2.4 ppm

• 6.4 ppm

• 3.6 ppm

• 3.2 ppm