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Zorluk: OrtaTypes and Preparation Methods of Salts

In the laboratory preparation of zinc tetraoxosulfate(VI) crystals (ZnSO4⋅7H2OZnSO_4 \cdot 7H_2O) from dilute tetraoxosulfate(VI) acid (H2SO4H_2SO_4) and zinc metal, why is excess zinc metal added to the acid?

  1. To ensure all the acid is completely reacted so that the salt solution is not contaminated with acidCevap
  2. B
    To prevent the zinc tetraoxosulfate(VI) salt from undergoing hydrolysis in the aqueous solution
  3. C
    To act as a heterogeneous catalyst to increase the rate of crystallization
  4. D
    To convert the resulting normal salt into a basic salt by excess metal accumulation

Cevap

Excess zinc metal is added to ensure all the acid is completely reacted so that the salt solution is not contaminated with acid.
When preparing a soluble salt from an acid and an insoluble solid (such as a metal, oxide, or carbonate), the solid is added in excess to ensure that every molecule of acid reacts completely. Because both the acid and the formed salt are soluble in water, any unreacted acid would remain mixed with the salt during crystallization and contaminate the product. The excess solid metal is easily removed by filtration before evaporating the filtrate.

Adım Adım Çözüm

1
Identify the type of reaction and salt being prepared
Zinc tetraoxosulfate(VI) (ZnSO4ZnSO_4) is a soluble salt prepared by reacting a dilute acid (H2SO4H_2SO_4) with a moderately reactive insoluble metal (ZnZn).
Soluble salts of reactive metals are prepared by acid-metal reactions.
2
Analyze the separation and purification step
If acid remains in excess, it cannot be separated from the soluble salt solution by filtration or simple evaporation.
Both the salt and acid are soluble in water, so unreacted acid would contaminate the final crystalline product.
3
Determine the role of adding excess insoluble solid reactant
Adding excess zinc metal guarantees 100% consumption of the acid. The excess insoluble zinc can easily be filtered off, leaving a pure aqueous salt solution.
Insoluble solids are easy to separate from solutions via filtration.

Anahtar Kavram

Method of preparing soluble salts by reacting dilute acid with an excess of an insoluble metal, base, or trioxocarbonate(IV).
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Types and Preparation Methods of Salts

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