Suppose we used an organic and an aqueous solvent in solvent extraction. How do

Question

Suppose we used an organic and an aqueous solvent in solvent extraction. How do we know which layer in the separatory funnel is the organic layer and which is the aqueous layer? a. The organic layer is always on top of the aqueous layer b. The aqueous layer is always on top of the organic layer c. Smell the content of the separatory funnel d. Add a small drop of distilled water to the separatory funnel and determine which layer it merges with. The layer merged with is the aqueous layer. e. The solvent with the higher density is at the top of the separatory funnel Which of the following are possible solvent pair for solvent extraction? a. methanol and water b. toluene and benzene c. chloroform and dichloromethane d. pentane and water e. diethyl ether and ethyl acetate Which of the following is false regarding shaking the separatory funnel? a. to ensure complete mixing between the two layers b. to reach equilibrium faster in which the product distributes itself between the two layers c. to ensure efficient extraction d. to reduce foam (or emulsion) formation In recrystallization, addition of too much hot solvent results in a. less product yield b. smaller crystal size c. bigger crystal size d. faster cooling time e. none of the above In recrystallization, there were two filtrations done in the procedure. The first filtration involves filtering while solution is hot, while a latter filtration involves filtering when the solution is already cooled down. The first filtration gets rid of _____ impurities, while the second filtration gets rid of _____ impurities. a. insoluble impurities;soluble impurities b. insoluble impurities;insoluble again c. soluble impurities;insoluble impurities d. soluble impurities;soluble impurities e. both soluble and insoluble impurities;both soluble and insoluble impurities again In recrystallization, why do we cool the first filtrate slowly? a. to obtain more crystals b. to obtain bigger crystals c. to prevent soluble impurities from precipitation d. to prevent insoluble impurities from precipitation e. A and B What is occlusion? a. the amount of supersaturation a solution undergo b. trapped impurities within the crystal lattice c. adsorbed impurities on the surfaces of crystal lattice d. the process in which a solution turns cloudy e. the phenomenon where a solution fails to recrystallize What is the main reason why impurities are sometimes trapped inside a crystal lattice? a. cooling the solution too quickly b. failure to filter using a fluted filter paper c. failure to wash the crystals with enough cold water d. leaving the crystals too long in the solution (after the first filtration) e. diffusion of impurities into the interior of the crystal Why do we wash the desired crystals with cold solvent during the second filtration? a. to get rid of adsorbed impurities on the surface of the desired crystals b. to prevent occlusion c. to obtain bigger crystals d. to isolate the insoluble impurities e. to increase product yield

Explanation / Answer

20. The organic phase is heavier than the aqueous, so the organic will be the lower phase.

21. Chloroform and dichloromethane

22. The false statement is: To reduce foam (or emulsion) formation.

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