Final answer:
Potash alum KAl(SO₄)₂·12H₂O is an example of a double salt, which is formed from the combination of potassium sulfate and aluminum sulfate. Such salts dissociate completely into their constituent ions in water, unlike basic, acidic, or normal salts which generally originate from a single acid or base. The correct option is D.
Step-by-step explanation:
Potash alum KAl(SO₄)₂·12H₂O is an example of a double salt. Double salts are those which are formed by a combination of two simple salts and crystallize together as a single material. In the case of potash alum, it is formed from the combination of potassium sulfate and aluminum sulfate and includes 12 molecules of water of hydration. Double salts dissociate completely into their constituent ions when they are dissolved in water.
When determining whether salts are acidic, basic, or neutral in aqueous solutions, we usually consider the strength of the acids and bases the ions come from. For example:
- KBr, which comes from KOH (a strong base) and HBr (a strong acid), will form a neutral solution.
- NaHCO₃, which comes from NaOH (a strong base) and H₂CO₃ (a weak acid), will form a basic solution, thus making it a basic salt.
In the example provided, KAl(SO₄)₂·12H₂O does not fit the definitions of a basic salt, acidic salt, or normal salt because it is composed of two different salts; hence, it is a double salt.