Question

Which of the following tests is used to detect presence of oxygen in organic compounds?
(A) Duma’s method
(B) Kjeldahl’s method
(C) Carius method
(D) Indirect interference

Answer 1

Hint : Presence of oxygen in organic compounds cannot be detected by direct method. We can only detect it in the form of a functional group. The functional group reacts with specialised reagent to give oxygen containing compounds.

Complete Step By Step Answer:
Duma’s method- Duma’s method is used for the detection of molecular weight of unknown substances. It is mainly used for detection of molecular mass of volatile organic compounds. In this method we take a small sample of unknown substance in a closed vessel and heat it until it is completely converted into vapour form. We take an assumption that the vapour form behaves ideally and use an ideal gas equation for the calculation of the number of moles.
Kjeldahl method- This method is used to determine nitrogen in organic compounds as well in inorganic compounds. This method includes heating of a sample at ${360^ \circ } - {410^ \circ }C$ in presence of sulphuric acid which decomposes the organic sample. Nitrogen is reduced to ammonium sulphate and carbon and sulphur is oxidised by concentrated sulphuric acid. Ammonium ion is concentrated in the acidic solution so the amount of nitrogen now can be measured by titration.
Carius method- This method is used to detect halogen in chemical substances. In this method a sample of organic substance is heated in presence of fuming nitric acid and silver nitrate in a hard glass tube known as carius tube. Carbon and hydrogen present in the compound is oxidised to carbon dioxide and water respectively and halogen is precipitate out as silver halides
Indirect interference- this method is used to detect oxygen by indirect method. In which we use different reactions of functional groups for detection of oxygen.
Hence the correct option is D.

Note :
Oxygen can also detect when a substance decomposes to form water that indicates the presence of oxygen. Oxygen in organic compounds mainly present in functional groups.