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Zorluk: OrtaFiltration, Evaporation, and Crystallization

What is the correct sequential order of laboratory steps required to obtain pure, dry copper(II) sulfate crystals from a mixture of solid copper(II) sulfate and insoluble sand?

  1. 1Add distilled water to the solid mixture and stir thoroughly.
  2. 2Filter the mixture using a funnel and filter paper.
  3. 3Gently heat the filtrate in an evaporating dish until it reaches saturation.
  4. 4Allow the hot saturated solution to cool gradually at room temperature.
  5. 5Filter off the formed crystals and dry them gently between sheets of filter paper.

Cevap

The correct sequence begins with dissolving the soluble component in water, filtering to remove insoluble sand, heating the filtrate to obtain a saturated solution, cooling gradually to precipitate pure crystals, and finally filtering and drying the isolated crystals.
The purification of a mixture containing a soluble salt and an insoluble impurity requires dissolving the salt in water first, followed by filtration to remove the insoluble residue. To obtain pure crystals, the filtrate must be heated only until saturated and then allowed to cool slowly, as rapid or total evaporation to dryness destroys hydrated crystals. Finally, filtering and blotting the crystals isolates pure, dry hydrated salt.

Adım Adım Çözüm

1
Dissolve the mixture in water.
Copper(II) sulfate dissolves into solution while sand remains solid.
Exploits the differential solubility of the two components.
2
Filter the suspension.
Sand is retained on the filter paper as residue; clear copper(II) sulfate solution passes through as filtrate.
Filtration physically separates an insoluble solid from a liquid.
3
Evaporate partially to crystallizing point.
A hot saturated solution is formed.
Evaporating to dryness would decompose the hydrated salt into an anhydrous powder.
4
Cool the saturated solution.
Pure copper(II) sulfate crystals precipitate from the solution.
Solubility of most solid solutes decreases as temperature falls.
5
Isolate and dry the crystals.
Pure, dry crystals of hydrated copper(II) sulfate are obtained.
Filtration collects the solid crystals, and drying with filter paper removes residual moisture without removing water of crystallization.

Anahtar Kavram

Multi-step purification of soluble and insoluble solid mixtures via selective dissolution, filtration, evaporation to saturation, and crystallization.
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