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Principles Related to Practical Chemistry · Question 24

NEET 2013 (Karnataka)MCQEasy📈 Topic in 38% papers+4−1
1

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

Answer

(2) Fe4[Fe(CN)6]3

Solution

Sodium fusion converts N into NaCN, which with FeSO4 gives sodium hexacyanidoferrate(II):

6CN- + Fe2+ [Fe(CN)6]4-

On heating with conc. H2SO4, some Fe2+ is oxidised to Fe3+:

3[Fe(CN)6]4- + 4Fe3+ Fe4[Fe(CN)6]3 xH2O

As per NCERT, the Prussian blue colour confirms nitrogen.

Answer: (2)

NEET 2013 (Karnataka)

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2

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)
3

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)
4

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
5

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
6

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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All NEET Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolid StateSolutionsElectrochemistryChemical KineticsSurface Chemistry
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureHydrogens-Block Elementsp-Block Elements (Group 13 & 14)Environmental ChemistryGeneral Principles of Isolation of Elementsp-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPolymersChemistry in Everyday LifePrinciples Related to Practical Chemistry