Determining Dissolved Oxygen Levels in Sewage Treatment Plant Water

The video tutorial explains the process of determining dissolved oxygen (DO) in a sample using a series of chemical reactions. It begins with the preparation of reagents and the filling of a BOD bottle with sewage treatment plant water. Reagents such as manganese sulphate and alkali iodide are added, and the mixture is stirred to remove air bubbles. After precipitation, concentrated sulphuric acid is added, turning the solution dark straw-colored. The sample is then titrated with sodium thiosulphate until it becomes colorless, with starch used as an indicator. The volume of thiosulphate consumed is recorded to calculate the DO level.

What is the primary objective of the experiment discussed in the video?

• To calculate the turbidity of water

• To measure the pH level of water

• To find the concentration of nitrates in water

• To determine the dissolved oxygen (DO) in water

Which reagent is NOT mentioned as being prepared for the experiment?

• Hydrochloric acid

• Alkali iodide azide

• Manganese sulphate

• Starch indicator

What type of water sample is used in the experiment?

• Rainwater

• Sewage treatment plant water

• Tap water

• Distilled water

How much manganese sulphate is added to the sample?

• 4 ml

• 1 ml

• 2 ml

• 3 ml

What is the purpose of mixing the sample well before titration?

• To change the color of the solution

• To increase the temperature

• To eliminate air bubbles

• To dissolve the reagents completely

What color does the solution turn after adding concentrated sulphuric acid?

• Clear

• Dark straw

• Light blue

• Pale yellow

How much sample is measured from the BOD bottle for titration?

• 250 ml

• 203 ml

• 150 ml

• 100 ml

What is the role of starch in the titration process?

• To increase the reaction rate

• To act as a catalyst

• To neutralize the solution

• To indicate the endpoint

What color change indicates the completion of the titration?

• Colorless to dark blue

• Dark blue to colorless

• Dark straw to pale yellow

• Pale yellow to dark straw

What is recorded to determine the amount of dissolved oxygen?

• The initial color of the solution

• The volume of sodium thiosulphate used

• The temperature of the solution

• The pH level of the solution