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Principles Related to Practical Chemistry

JEE Main 2024 (Online) 29th January Evening ShiftMCQEasy📈 Topic in 41% papers+4−1
Ques. 1JEE Main 2024, 29 January (Evening Shift)

On passing a gas, 'X', through Nessler's reagent, a brown precipitate is obtained. The gas 'X' is

  1. Cl2
  2. CO2
  3. NH3
  4. H2S

Answer

(3) NH3

Solution

Nessler's reagent = alkaline K2HgI4; it is the test for NH3 / NH4+:

2K2HgI4 + NH3 + 3KOH

brown pptHgO Hg(NH2)I + 7KI + 2H2O

∵ the brown precipitate (iodide of Millon's base) is given only by NH3 ⇒ X = NH3

Cl2, CO2, H2S give no brown precipitate.

Answer: (3)

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Ques. 2JEE Main 2024, 29 January (Evening Shift)

Chromatographic technique/s based on the principle of differential adsorption is / are Choose the most appropriate answer from the options given below:

  1. B only
  2. A only
  3. A & B only
  4. C only
Ques. 3JEE Main 2024, 29 January (Evening Shift)

A reagent which gives brilliant red precipitate with Nickel ions in basic medium is

  1. dimethyl glyoxime
  2. sodium nitroprusside
  3. meta-dinitrobenzene
  4. neutral FeCl3
Ques. 4JEE Main 2024, 29 January (Evening Shift)

The oxidation number of iron in the compound formed during brown ring test for NO3- ion is .

Ques. 5JEE Main 2024, 27 January (Morning Shift)

Yellow compound of lead chromate gets dissolved on treatment with hot NaOH solution. The product of lead formed is a :

  1. Tetraanionic complex with coordination number six
  2. Neutral complex with coordination number four
  3. Dianionic complex with coordination number six
  4. Dianionic complex with coordination number four
Ques. 6JEE Main 2024, 27 January (Morning Shift)

NaCl reacts with conc. H2SO4 and K2Cr2O7 to give reddish fumes (B), which react with NaOH to give yellow solution (C). (B) and (C) respectively are ;

  1. CrO2Cl2, Na2CrO4
  2. Na2CrO4, CrO2Cl2
  3. CrO2Cl2, KHSO4
  4. CrO2Cl2, Na2Cr2O7
Ques. 7JEE Main 2024, 27 January (Evening Shift)

The technique used for purification of steam volatile water immiscible substances is :

  1. Fractional distillation
  2. Distillation
  3. Fractional distillation under reduced pressure
  4. Steam distillation
Ques. 8JEE Main 2024, 27 January (Evening Shift)

Phenolic group can be identified by a positive:

  1. Tollen's test
  2. Phthalein dye test
  3. Carbylamine test
  4. Lucas test

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