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Difficulty: MediumFiltration, Evaporation, and Crystallization

A solid mixture consists of insoluble silicon(IV) oxide (SiO2\text{SiO}_2) and soluble potassium tetraoxosulfate(VI) (K2SO4\text{K}_2\text{SO}_4). After adding distilled water to the mixture and stirring thoroughly, which procedure should be used to separate the insoluble solid and obtain pure crystals of potassium tetraoxosulfate(VI)?

  1. Filter the mixture to remove SiO2\text{SiO}_2, then heat the filtrate to concentrate it before allowing it to cool and crystallize.Answer
  2. B
    Evaporate the entire mixture to complete dryness and collect the combined residue.
  3. C
    Perform fractional distillation on the suspension to collect K2SO4\text{K}_2\text{SO}_4 as the first distillate fraction.
  4. D
    Filter the mixture to collect K2SO4\text{K}_2\text{SO}_4 on the filter paper while SiO2\text{SiO}_2 passes into the filtrate.

Answer

Filtration of the mixture to remove the insoluble silicon(IV) oxide (SiO2\text{SiO}_2), followed by partial evaporation of the filtrate to concentrate it and subsequent cooling to allow potassium tetraoxosulfate(VI) (K2SO4\text{K}_2\text{SO}_4) crystals to form.
Filtration successfully separates the insoluble silicon(IV) oxide (SiO2\text{SiO}_2) as the residue on the filter paper from the soluble potassium tetraoxosulfate(VI) (K2SO4\text{K}_2\text{SO}_4) in the filtrate. Heating the filtrate to concentrate it and then letting it cool slowly yields pure crystals of the salt.

Step-by-Step Solution

1
Dissolve the mixture in water and filter the suspension.
Insoluble silicon(IV) oxide (SiO2\text{SiO}_2) is retained on the filter paper as the residue, while dissolved potassium tetraoxosulfate(VI) (K2SO4\text{K}_2\text{SO}_4) passes through as the clear filtrate.
Filtration separates insoluble solids from liquids based on particle size and solubility.
2
Evaporate the filtrate partially until it reaches its crystallization point (saturated solution).
Excess solvent is driven off without decomposing the salt or trapping impurities.
Controlled evaporation concentrates the solution to saturation without heating to complete dryness.
3
Allow the hot saturated solution to cool slowly at room temperature.
Pure crystals of K2SO4\text{K}_2\text{SO}_4 form and deposit out of solution.
Solubility decreases with decreasing temperature, causing the solute to crystallize.

Key Concept

Separation of insoluble and soluble solid mixtures using filtration and crystallization
Estimated Time:1m 0s
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Topics

Filtration, Evaporation, and Crystallization