Question

Part B - Questions 1) Put the letter of the correct answer for each of the following questions in the box to the right. 10 points a. For a mixture of pure hexane and pure dimethylformamide, the dimethylformamide layer will be found as: (A) the top layer (B) the bottom layer (C) neither; the two (D) cannot determine solvents are miscible b. To extract aniline (C&H5NH2) from a solution of chloroform, one would use: (A) aqueous HCI (B) aqueous NaOH (C) aqueous NaHCO3 (D) either B or C would work c. For mixture of methylene chloride and diethyl ether, the diethyl ether layer will be found as: (A) the top layer (B) the bottom layer (C) neither, the two (D) cannot determine solvents are miscible d. To extract benzyl alcohol (CH CH2OH) from a solution of chloroform, one would use: (A) aqueous HCI (B) aqueous NaOH (C) aqueous NH3 (D) either B or C would work e. A large partition coefficient for the extraction of naphthalene into diethyl ether from water means that naphthalene will be found: (A) only in the water (B) only in the diethyl (c) mostly in the water (D) mostly in the layer ether layer layer diethyl ether layer

Answer 1

1.

(a) Hexane and Dimethyl Formamide (DMF) are Immiscible solvents , and incapable of mixing with each other , these separates out into a definite layer : Dimethyl Formamide (DMF) will be found as bottom layer , because its density is much more than Hexane. : B

(b) Aniline (C₆H₅NH₂) from chloroform can be extracted using HCl (aq) , as it will form salt (anilinium chloride ) with it :

C₆H₅NH₂ + HCl (aq) -------> C₆H₅NH₃⁺Cl^- (aq)

and will be in aqueous layer, which can be separated adding base. Since aniline is a base it cannot be separated using base like NaOH or NaHCO₃ . A

(c) A mixture of Methylene Chloride (CH₂Cl₂ ) and Diethyl ether (H₅C₂-O-OC₂H₅) are miscible with other , and mix with each other , these do not separates out as a definite layer. Since, Both are non-polar solvents so miscible with other. C

(d)

Benzyl alcohol (C₆H₅OH) from chloroform can be extracted using NaOH (aq) , as it will form alkoxide with it :

C₆H₅OH + NaOH (aq) -------> C₆H₅O^- Na⁺ (aq)

and it will be in aqueous layer, which can be separated adding acid. It cannot be separated using acid as it is a weak acid and ammonia is a weak base to give alkoxide . B

(e) A large partition coefficient for extraction of Naphthalene in Diethyl ether  from water , means Naphthalene will be mostly in Diethyl ether layer : D