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MCQEasyJEE 2025Quantitative Analysis (C, H, N…)

JEE Chemistry 2025 Question with Solution

Given below are two statements I and II.

Statement I: Dumas method is used for estimation of "Nitrogen" in an organic compound.

Statement II: Dumas method involves the formation of ammonium sulfate by heating the organic compound with concentrated H2SO4\mathrm{H_2SO_4}.

In the light of the above statements, choose the correct answer from the options given below:

  • A

    Both Statement I and Statement II are true

  • B

    Statement I is false but Statement II is true

  • C

    Both Statement I and Statement II are false

  • D

    Statement I is true but Statement II is false

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: Two statements about Dumas method are to be checked.

Find: Which option correctly identifies the truth value of Statement I and Statement II.

Statement I says that Dumas method is used for estimation of nitrogen in an organic compound. This is true. In Dumas method, the organic compound is heated in the presence of excess oxygen, and the nitrogen present is converted into nitrogen gas, N2\mathrm{N_2}, which is measured.

Statement II says that Dumas method involves the formation of ammonium sulfate by heating the organic compound with concentrated H2SO4\mathrm{H_2SO_4}. This is false. Formation of ammonium sulfate by digestion with concentrated sulfuric acid is a feature of Kjeldahl method, not Dumas method.

Therefore, Statement I is true and Statement II is false.

The correct option is D.

Comparison with Kjeldahl Method

Given: The question compares the description of Dumas method with the process involving concentrated H2SO4\mathrm{H_2SO_4}.

Find: Whether each statement is true or false.

In the Dumas method, nitrogen estimation is carried out by converting the nitrogen of the organic compound into gaseous N2\mathrm{N_2} and then measuring that gas quantitatively. Hence, Statement I is correct.

The process of heating an organic compound with concentrated H2SO4\mathrm{H_2SO_4} to convert nitrogen into ammonium sulfate belongs to the Kjeldahl method. Therefore, Statement II incorrectly describes Dumas method.

So, the final conclusion is that Statement I is true but Statement II is false, and the correct option is D.

Common mistakes

  • Confusing Dumas method with Kjeldahl method. This is wrong because ammonium sulfate formation with concentrated H2SO4\mathrm{H_2SO_4} is specific to Kjeldahl estimation. Instead, remember that Dumas method estimates nitrogen by measuring evolved N2\mathrm{N_2} gas.

  • Assuming that any nitrogen estimation method in organic chemistry uses sulfuric acid digestion. This is incorrect because different methods use different principles. Identify the method first, then match its characteristic steps.

  • Reading Statement I too narrowly and thinking Dumas method is not used for nitrogen estimation. This is wrong because Dumas method is a standard quantitative method for estimating nitrogen in organic compounds. Focus on the core purpose of the method.

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