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Kjeldahl's Method - Practice Questions & MCQ
Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main
Quick Facts
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Kjeldahl's Method is considered one the most difficult concept.
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12 Questions around this concept.
Solve by difficulty
Kjeldahl's method cannot be used to estimate nitrogen for which of the following compounds?
For the estimation of nitrogen, 1.4 g of an organic compound was digested by Kjeldahl method and the evolved ammonia was absorbed in 60 mL of sulphuric acid. The unreacted acid required 20 mL of
sodium hydroxide for complete neutralization. The percentage of nitrogen in the compound is :
Directions: In the following questions, a statement of Assertion (A) is followed by a statement of reason (R).
Assertion: In Kjeldahi's method, the compound containg Nitrogen is heated with concentrated H2SO4.
Reason: Concentrated H2SO4 act as a dehydrating agent.
Mark the correct choice as:
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Given below are two statements :
Statement (I): The Kjeldahl method is applicable to estimate nitrogen in pyridine.
Statement (II) The nitrogen present in pyridine can easily be converted into ammonium sulfate in the Kjeldahl method.
In light of the above statements, choose the correct answer from the options given below.
Concepts Covered - 1
Kjeldahl's Method
The compound containing nitrogen is heated with concentrated sulphuric acid. Nitrogen in the compound gets converted to ammonium sulphate. The resulting acid mixture is then heated with excess of sodium hydroxide. The liberated ammonia gas is absorbed in an excess of standard solution of sulphuric acid. The amount of ammonia produced is determined by estimating the amount of sulphuric acid consumed in the reaction. It is done by estimating unreacted sulphuric acid left after the absorption of ammonia by titrating it with standard alkali solution. The difference between the initial amount of acid taken and that left after the reaction gives the amount of acid reacted with ammonia.
Kjeldahl method is not applicable to compounds containing nitrogen in nitro and azo groups and nitrogen present in the ring (e.g. pyridine) as nitrogen of these compounds does not change to ammonium sulphate under these conditions.
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