3) For recrystallization of 3g impure naphthalene (2.7g pure naphthalene inside)

Question

3) For recrystallization of 3g impure naphthalene (2.7g pure naphthalene inside), one student get only 0.5g product. Why? Choose 5 reasons which may lead to the low yield, from the 10 choice given to you below. (10pts) A) After mixing of the impure naphthalene and solvent, the heating time is long. 8) After mixing of the impure naphthalene and solvent, the heating temperature is low. C) When doing the gravity filtration, the filtering paper is fluted D) When doing the gravity filtration, the solution is hot. E) When drying the solution the CaCl was not enough. F) After decanting the mixture, there was some liquid left. G) When doing the suction filtration, the solution was hot H) When doing the suction filtration, the filter paper is fluted 1) When doing the suction filtration, the vacuum is not good. J) When doing the suction filtration, ether was used to wash the filter cake.

Explanation / Answer

B) After mixing of the impure naphtalene and solvent, the heating time temperature is low, if heating temperature is lower then the substance does not disolve properly and hence low yield of purity.

D) When doing Gravity filteration, the solution is hot, because in purification impure should be heated to make clear hot solution and aloow to cool to room temperature to form crystals. if we do filatertion of hot solution then we get lower yield.

(E) When drying the solution the CaCl2 was not enough, because CaCl2 is a drying agent if it is not sufficient moisture in solvents allows to loose the purity yield.

G) When doing suction filteration, the solution was hot, reason explained in pervious point (D)

J) when doing the suction filteration, ether was used to wash the filter cake because Naphthalene readily soluble in solvents like ether, chloroform, carbon disulphide etc.

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