Top 10 viva/interview Questions on Chemical Oxygen Demand or COD test

Chemical Oxygen Demand (COD) determines the quantity of oxygen required to oxidize the organic matter in water  or  waste  water  sample,  under  specific  conditions  of  oxidizing  agent, temperature, and time.

The  chemical  oxygen  demand  (COD)  test  is  commonly  used  to  indirectly  measure  the  amount  of  organic  compounds  in  water. 

Most  applications  of  COD  determine the amount of organic pollutants found in surface water (e.g. lakes and rivers),  making  COD  a  useful  measure  of  water  quality.  It  is  expressed  in  milligrams  per  liter  (mg/L),  which  indicates  the  mass  of  oxygen consumed per liter of solution.

1.Potassium dichromate is considered as the best

a)  Oxidizing agent
b)  Reducing agent
c)  Redox agent
d)  Chemical agent

2.Mercury Sulphate is added to reduce the interference of

a)  Chlorides.
b)  Sulphates
c)  Organic pollutants
d)  Hardness

3.Silver Sulphate is added as

a)  Oxidizing agent
b)  Reducing agent
c)  Redox agent
d)  Catalyst

4.Ferroin indicator is

a)  Phenanthroline mono hydrate 
b)  Ferric sulphate
c)  Phenanthroline mono hydrate and Ferric Sulphate
d)  Ferrous Sulphate

5.After refluxing, ___________ solution is titrated against FAS.

a)  excesspotassium dichromate
b)  consumed potassium dichromate
c)  initially added potassium dichromate
d)  potassium dichromate and silver sulphate

6. H2SO4 is added to FAS solution

a)  as it is a component of the reagent
b)  to prevent hydrolysis of ferrous sulphate into ferrous hydroxide
c)  to provide acidic medium
d)  to neutralise the medium

7.  The products formed after Chemical Oxygen Demand COD analysis are ______.

a)  Carbon di oxide and water
b)  Water alone
c)  Carbon di oxide alone
d)  Carbon monoxide and water

8.In industrial waste water, COD value is about _____________ BOD value.

a)  2.5 times
b)  3.5 times
c)  4.5 times
d)  5.5 times

9. Sulphuric acid is added

a)   as it assists in oxidizing the nitrogen compounds
b)   to provide acidic medium
c)   to neutralise the medium
d)   as catalyst

10. A blank solution is

a)  identical in all respects to the test solution except for the absence of test solute
b)  identical in all respects to the test solution
c)  a solution without any reagents
d)  a solution without distilled water

Recommended For You:

• Top 10 Viva/interview questions on Dissolved Oxygen Test
• Top 10 viva/interview questions on Biological Oxygen Demand (BOD) test
• Top 10 viva/interview Questions on Turbidity Test
• Top 10 viva/interview questions on Acidity of wastewater test
• Top 10 viva/interview questions on Hardness of wastewater test
• Top 10 viva/interview questions on pH value of wastewater test
• http://civildelights.blogspot.com/2017/04/top-10-viva/interviewquestions-on-chlorides-contents.html