Question

1. What class of molecules is responsible for most of the reducing power in natural waters? What parameter is a measure of that reducing power?

2. Five hundred kg of n-propanol (CH3CH2CH2OH) are accidentally discharged into a body of water containing 108 liters of H2O. By how much is the BOD (in mg O2 per liter) of this water increased? Assume the following reaction: CH3CH2CH2OH + 9/2O2 = 3CO2 + 4H2O

3. What is COD, chemical oxygen demand? What is the primary reason that sometimes COD is used in place of BOD?

Answer 1

1. Natural water contains anions such as chloride, carbonate, bicarbonate and sulfate etc. which are responsible for reducing properties.

2. 500 kg of n-propanol= 500000/60.09=8320 mol

mol of water=108000/18=6000 mol

1 mol of n-propanol reacts with 4.5 mol of oxygen and produces 3 mol of CO2.

amount of dissolved oxygen vary with temperature and also with salt concentration like natural and sea water.

so more information is needed about condition.

3. If oxygen demand is increased due to chemicals present in water i.e. COD. For eg- In the above question O2 demand in increasing due to n-propanol.