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Principles Related to Practical Chemistry

JEE Main 2024 (Online) 29th January Evening ShiftNumericalEasy📈 Topic in 20% papers+4
Ques. 1JEE Main 2024, 29 January (Evening Shift)

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

Answer

1

Solution

NO3- + 3Fe2+ + 4H+ NO + 3Fe3+ + 2H2O

[Fe(H2O)6]2+ + NO [Fe(H2O)5(NO)]2+ + H2O (brown ring)

∵ NO is bonded as NO+: x + 0 + (+1) = +2 ⇒ x = +1

Answer: 1

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Ques. 2JEE 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. 3JEE 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. 4JEE 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. 5JEE 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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