Question Video: Identifying the Best Method to Separate the Products in the Reaction of Cadmium Sulfate and Potassium Sulfide | Nagwa Question Video: Identifying the Best Method to Separate the Products in the Reaction of Cadmium Sulfate and Potassium Sulfide | Nagwa

Question Video: Identifying the Best Method to Separate the Products in the Reaction of Cadmium Sulfate and Potassium Sulfide Chemistry • Third Year of Secondary School

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Consider the following reaction: CdSO₄(aq) + K₂S(aq) ⟶ CdS(s) + K₂SO₄(aq) By which of the following methods are the reaction products most easily separated? [A] Crystallization method [B] Distillation method [C] Filtration method [D] Titration method [E] Volatilization method

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Video Transcript

Consider the following reaction: CdSO4, aqueous, plus K2S, aqueous, react to produce CdS, solid, plus K2SO4, aqueous. By which of the following methods are the reaction products most easily separated? (A) Crystallization method, (B) distillation method, (C) filtration method, (D) titration method, or (E) volatilization method.

The reaction begins with two aqueous compounds: cadmium sulfate and potassium sulfide. When these aqueous solutions are combined, they produce potassium sulfate, a compound soluble in water, and cadmium sulfide, a compound insoluble in water. Potassium sulfate, being soluble, remains dissolved in the solution, while cadmium sulfide, being insoluble, forms a precipitate. So, the end product of this reaction is an insoluble solid and a liquid.

Now, what is the best method of separating a liquid from a solid? Filtration and crystallization are the only methods listed that traditionally separate a solid and a liquid. Thus, we can eliminate answer choices (B), (D), and (E).

Filtration involves pouring the mixture through a piece of filter paper to separate an insoluble solid from a liquid. The water and dissolved potassium sulfate will pass through the filter paper, while the solid cadmium sulfide will remain on the filter paper.

Crystallization, on the other hand, involves heating the water off, which would leave both the cadmium sulfide and the potassium sulfate in the test tube, as neither of them will evaporate. Crystallization is used to separate a liquid from a soluble solid, whereas we have a liquid and an insoluble solid.

Thus, of the methods given, the one which will most easily separate the reaction products is (C), filtration method.

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