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Principles Related to Practical Chemistry

JEE Main 2024 (Online) 31st January Evening ShiftMCQEasy📈 Topic in 42% papers+4−1
Ques. 1JEE Main 2024, 31 January (Evening Shift)

The fragrance of flowers is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in vapour phase. A suitable method for the extraction of these oils from the flowers is -

  1. distillation
  2. steam distillation
  3. distillation under reduced pressure
  4. crystallisation

Answer

(2) steam distillation

Solution

Steam distillation is used for a substance that is steam volatile and immiscible with water.

∵ The mixture boils when poil + pwater = patm ⇒ the oil distils below 373 K, without decomposing

(1): simple distillation needs the b.p. of the oil ⇒ oil may decompose ⇒ (1) is not suitable

(2): oil is steam volatile + water immiscible ⇒ (2) is suitable

(3): used for liquids that decompose at their b.p. (e.g. glycerol), not steam-volatile oils ⇒ (3) is not the best method

(4): crystallisation purifies solids ⇒ (4) is not suitable

Answer: (2)

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Ques. 2JEE Main 2024, 30 January (Morning Shift)

Given below are two statements : In the light of the above statements, choose the most appropriate answer from the options given below :

  1. Both Statement I and Statement II are false
  2. Statement I is true but Statement II is false
  3. Both Statement I and Statement II are true
  4. Statement I is false but Statement II is true
Ques. 3JEE Main 2024, 30 January (Morning Shift)

The Lassaigne's extract is boiled with dil HNO3 before testing for halogens because,

  1. Silver halides are soluble in HNO3.
  2. AgCN is soluble in HNO3.
  3. Na2S and NaCN are decomposed by HNO3.
  4. Ag2S is soluble in HNO3.
Ques. 4JEE Main 2024, 30 January (Morning Shift)

On a thin layer chromatographic plate, an organic compound moved by 3.5 cm, while the solvent moved by 5 cm. The retardation factor of the organic compound is 10-1.

Ques. 5JEE Main 2024, 30 January (Evening Shift)

Which among the following purification methods is based on the principle of "Solubility" in two different solvents?

  1. Distillation
  2. Sublimation
  3. Column Chromatography
  4. Differential Extraction
Ques. 6JEE Main 2024, 30 January (Evening Shift)

Number of metal ions characterized by flame test among the following is . Sr2+, Ba2+, Ca2+, Cu2+, Zn2+, Co2+, Fe2+

Ques. 7JEE Main 2024, 29 January (Morning Shift)

In chromyl chloride test for confirmation of Cl- ion, a yellow solution is obtained. Acidification of the solution and addition of amyl alcohol and 10\% H2O2 turns organic layer blue indicating formation of chromium pentoxide. The oxidation state of chromium in that is

  1. +6
  2. +5
  3. +3
  4. +10
Ques. 8JEE Main 2024, 29 January (Morning Shift)

Appearance of blood red colour, on treatment of the sodium fusion extract of an organic compound with FeSO4 in presence of concentrated H2SO4 indicates the presence of element/s

  1. Br
  2. S
  3. N and S
  4. N
Ques. 9JEE 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
Ques. 10JEE 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. 11JEE 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

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