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Principles Related to Practical Chemistry · Question 19

NEET (UG) 2022MCQEasy📈 Topic in 25% papers+4−1
1

The Kjeldahl's method for the estimation of nitrogen can be used to estimate the amount of nitrogen in which one of the following compounds?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(3) [figure]

Solution

As per NCERT, Kjeldahl's method is not applicable to compounds containing nitrogen in nitro and azo groups and nitrogen present in the ring (e.g. pyridine), because their nitrogen does not change to ammonium sulphate under the conditions of the method.

Nitrobenzene (nitro group), pyridine (ring nitrogen) and azobenzene (azo group) are therefore excluded.

Aniline has an -NH2 group ⇒ its nitrogen is converted to (NH4)2SO4 on heating with conc. H2SO4, so it can be estimated.

Answer: (3)

NEET (UG) 2022

Keep practising — Principles Related to Practical Chemistry

2

Paper chromatography is an example of :

  1. Partition chromatography
  2. Thin layer chromatography
  3. Column chromatography
  4. Adsorption chromatography
NEET (UG) 2020
3

The most suitable method of separation of 1 : 1 mixture of ortho and para-nitrophenols is

  1. chromatography
  2. crystallisation
  3. steam distillation
  4. sublimation.
NEET 2017
4

In Dumas method for estimation of nitrogen, 0.25 g of an organic compound gave 40 mL of nitrogen collected at 300 K temperature and 725 mm pressure. If the aqueous tension at 300 K is 25 mm, the percentage of nitrogen in the compound is

  1. 16.75
  2. 15.76
  3. 17.36
  4. 18.20
AIPMT 2015 (Cancelled)
5

In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1 M H2SO4. The percentage of nitrogen in the soil is

  1. 37.33
  2. 45.33
  3. 35.33
  4. 43.33
AIPMT 2014
6

Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour formed corresponds to which of the following formulae?

  1. Fe3[Fe(CN)6]2
  2. Fe4[Fe(CN)6]3
  3. Fe4[Fe(CN)6]2
  4. Fe3[Fe(CN)6]3
NEET 2013 (Karnataka)
7

The Lassaigne's extract is boiled with conc. HNO3 while testing for halogens. By doing so it

  1. decomposes Na2S and NaCN, formed
  2. helps in the precipitation of AgCl
  3. increases the solubility product of AgCl
  4. increases the concentration of NO3- ions
AIPMT 2011 (Prelims)
8

In Dumas method of estimation of nitrogen, 0.35 g of an organic compound gave 55 mL of nitrogen collected at 300 K temperature and 715 mm pressure. The percentage composition of nitrogen in the compound would be (aqueous tension at 300 K = 15 mm).

  1. 15.45
  2. 16.45
  3. 17.45
  4. 14.45
Out of syllabusAIPMT 2011 (Prelims)
9

The best method for the separation of naphthalene and benzoic acid from their mixture is

  1. distillation
  2. sublimation
  3. chromatography
  4. crystallisation.
AIPMT 2005
10

Which of the following is incorrect?

  1. FeCl3 is used in detection of phenol.
  2. Fehling's solution is used in detection of glucose.
  3. Tollens' reagent is used in detection of unsaturation.
  4. NaHSO3 is used in detection of carbonyl compound.
AIPMT 2001
11

In steam distillation of toluene, the pressure of toluene in vapour is

  1. equal to pressure of barometer
  2. less than pressure of barometer
  3. equal to vapour pressure of toluene in simple distillation
  4. more than vapour pressure of toluene in simple distillation.
AIPMT 2001

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