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Difficulty: MediumTypes and Preparation Methods of Salts

Complete the following statement regarding salt classification and laboratory preparation methods by filling in the missing terms.

Answer:Potash alum, KAl(SO4)2⋅12H2OKAl(SO_4)_2 \cdot 12H_2O, is classified as a 【double】 salt because it completely dissociates in water into all its constituent simple ions, whereas an insoluble salt like lead(II) sulfate (PbSO4PbSO_4) is prepared in the laboratory using 【double decomposition】.

Answer

The first blank is 'double' (or 'double salt') and the second blank is 'double decomposition' (or 'precipitation').
Potash alum dissociates into K+K^+, Al3+Al^{3+}, and SO42−SO_4^{2-} ions in solution, making it a double salt. Lead(II) sulfate (PbSO4PbSO_4) is insoluble in water and must be prepared by double decomposition (precipitation) by combining two aqueous solutions containing the requisite ions.

Step-by-Step Solution

1
Identify the classification of potash alum
Potash alum, KAl(SO4)2⋅12H2OKAl(SO_4)_2 \cdot 12H_2O, contains two different cations (K+K^+ and Al3+Al^{3+}) and ionizes completely into simple ions in aqueous solution, which defines a double salt.
Double salts retain the chemical properties of their constituent individual salts when dissolved in water, unlike complex salts which form complex ions.
2
Determine the appropriate laboratory preparation method for lead(II) sulfate (PbSO4PbSO_4)
Since PbSO4PbSO_4 is an insoluble salt, it is prepared by mixing solutions of two soluble salts containing Pb2+Pb^{2+} and SO42−SO_4^{2-} ions respectively.
Insoluble salts are synthesized via precipitation (double decomposition) reactions.

Key Concept

Classification of salts (double salts vs complex salts) and preparation of insoluble salts via precipitation/double decomposition.
Estimated Time:1m 0s
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Types and Preparation Methods of Salts

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