Dissolved oxygen

In what form does oxygen exist in water?

• Nascent oxygen

• Molecular state

• Combined with hydrogen

A low dissolved oxygen content in water indicates

• High level of pollution in water

• Low level of pollution

• Not related to pollution level

Why is manganese sulphate added to the solution?

• To dissolve the precipitate

• To convert molecular oxygen into precipitate form

• To get correct end point

Why is azide added to the solution?

• To remove the interference due to nitrites

• To convert molecular oxygen into a precipitate

• To carry out the titration effectively

What is the colour change for the titration?

• Blue to colourless

• Colourless to blue

• Yellow to Blue

• Blue to yellow

The method used for determination of dissolved oxygen is called as

• Iodimetric method

• Wrinkler method

• Alsterberg method

• Volumetric method

Why is sulphuric acid added during the titration?

• To increase the acidity of the solution

• To get an accurate end point

• To dissolve the precipitate and release nascent oxygen

What is the formula for the brown precipitate formed?

• Mn(OH)2

• MnO(OH)2

• MnSO4

• Mn(OH)3

What is the indicator used in this titration?

• No indicator used

• Starch

• Phenolphthalein

• Iodine acts as self indicator

Why does the solution give a dark yellow colour?

• Due to the presence of manganese hydroxide

• Due to the addition of sulphuric acid

• Due to the formation of iodine

• Due to the addition of hypo solution