JEE Chemistry Organic Chemistry Some Basic Principles and Techniques MCQs Set 54

Answer: (b) Sodium bicarbonate

Explanation:
1. The carboxylic acid is strong enough to react with bicarbonate and goes into water as its salt.
2. The phenol is weaker than carbonic acid and does not react with bicarbonate, while NaOH would dissolve both.

Teacher's Note:
1. Recall the standard fact.
2. The carboxylic acid is strong enough to react with bicarbonate and goes into water as its salt.

Answer: (a) Phenol and benzophenone

Explanation:
1. Phenol (acidic) dissolves in NaOH; a ketone such as benzophenone does not and gives the 2,4-DNP derivative.
2. Benzoic acid and phenol would both dissolve, and aniline gives no 2,4-DNP test.

Teacher's Note:
1. Recall the standard fact.
2. Phenol (acidic) dissolves in NaOH; a ketone such as benzophenone does not and gives the 2,4-DNP derivative.

Answer: (c) An aliphatic amide and naphthalene

Explanation:
1. Lower aliphatic amides are water soluble and are hydrolysed by hot NaOH to give ammonia.
2. Naphthalene is insoluble in water and sublimes.

Teacher's Note:
1. Recall the standard fact.
2. Lower aliphatic amides are water soluble and are hydrolysed by hot NaOH to give ammonia.

Answer: (c) Anisole

Explanation:
1. Phenols and carboxylic acids are acidic.
2. Anisole is an ether with no acidic hydrogen.

Teacher's Note:
1. Recall the standard fact.
2. Phenols and carboxylic acids are acidic.

Answer: (a) Fractional distillation

Explanation:
1. A fractionating column gives many successive vaporisation-condensation steps.
2. Vacuum distillation is for liquids decomposing near their boiling points.

Teacher's Note:
1. Recall the standard fact.
2. A fractionating column gives many successive vaporisation-condensation steps.

Answer: (d) Tetrahydrofuran

Explanation:
1. Oxygen is more electronegative than nitrogen, so the C-O dipoles are larger than the C-N dipoles in ring compounds of similar shape.
2. Cyclopentane and pentane are nearly non-polar.

Teacher's Note:
1. Recall the standard fact.
2. Oxygen is more electronegative than nitrogen, so the C-O dipoles are larger than the C-N dipoles in ring compounds of similar shape.

Answer: (b) The cis isomer has the higher dipole moment and boiling point

Explanation:
1. In the trans isomer the two C-Cl dipoles cancel (zero dipole moment).
2. The cis isomer is polar, so its boiling point is higher (about 333 K against about 321 K).

Teacher's Note:
1. Recall the standard fact.
2. In the trans isomer the two C-Cl dipoles cancel (zero dipole moment).

Answer: (b) Lower boiling point and lower water solubility

Explanation:
1. Ortho-nitrophenol has intramolecular hydrogen bonding, so it does not associate with other molecules or water.
2. p-Nitrophenol forms intermolecular hydrogen bonds, giving higher mp, bp and solubility.

Teacher's Note:
1. Recall the standard fact.
2. Ortho-nitrophenol has intramolecular hydrogen bonding, so it does not associate with other molecules or water.

Answer: (d) o-Nitrophenol and p-nitrophenol

Explanation:
1. The ortho isomer, with intramolecular hydrogen bonding, is steam volatile.
2. The para isomer, with intermolecular bonding, is not.

Teacher's Note:
1. Recall the standard fact.
2. The ortho isomer, with intramolecular hydrogen bonding, is steam volatile.

Answer: (a) p-Dichlorobenzene

Explanation:
1. The para isomer is the most symmetrical and packs best in the crystal, so it has the highest melting point (about 326 K).

Teacher's Note:
1. Recall the standard fact.
2. The para isomer is the most symmetrical and packs best in the crystal, so it has the highest melting point (about 326 K).

Answer: (c) Sublimation

Explanation:
1. Ammonium chloride sublimes on heating, while sodium chloride does not.
2. Both are soluble in water.

Teacher's Note:
1. Recall the standard fact.
2. Ammonium chloride sublimes on heating, while sodium chloride does not.

Answer: (d) Aniline forms a water-soluble salt

Explanation:
1. \( \ce{C6H5NH2 + HCl -> C6H5NH3+Cl-} \) is soluble in water.
2. Nitrobenzene is not basic and stays in the organic layer.

Teacher's Note:
1. Recall the standard fact.
2. \( \ce{C6H5NH2 + HCl -> C6H5NH3+Cl-} \) is soluble in water.

Answer: (b) Benzene < phenol < quinol < sodium terephthalate

Explanation:
1. Benzene is non-polar; phenol has one OH, quinol has two OH groups, and the sodium salt is ionic.
2. More hydrogen bonding or ionic character means higher solubility.

Teacher's Note:
1. Recall the standard fact.
2. Benzene is non-polar; phenol has one OH, quinol has two OH groups, and the sodium salt is ionic.

Answer: (a) Pentan-1-ol

Explanation:
1. Lower alcohols mix with water because of hydrogen bonding.
2. As the alkyl group grows, the hydrophobic part reduces solubility, so pentanol dissolves least.

Teacher's Note:
1. Recall the standard fact.
2. Lower alcohols mix with water because of hydrogen bonding.

Answer: (c) It passes directly from solid to vapour on heating, leaving non-volatile impurities

Explanation:
1. Anthracene vapours condense back to solid on cooling.

Teacher's Note:
1. Recall the standard fact.
2. Anthracene vapours condense back to solid on cooling.