Question

Which of the following is an example of double salt?

• A. Bleaching powder
• B. K$_4$[Fe(CN)$_6$]
• C. Hypo
• D. Potash alum

Hint:

Remember: Double salts lose their identity in solution, while coordination compounds retain their complex form.

Answer 1

The Correct Option is D

Step 1: Understanding double salts.
Double salts are crystalline salts obtained by the combination of two different salts. They dissociate completely into simple ions when dissolved in water.
Step 2: Analysis of options.
(A) Bleaching powder: A compound used as disinfectant, not a double salt.
(B) K$_4$[Fe(CN)$_6$]: This is a coordination compound, not a double salt.
(C) Hypo (Na$_2$S$_2$O$_3$·5H$_2$O): A simple hydrated salt, not a double salt.
(D) Potash alum: Correct — Potash alum (K$_2$SO$_4$·Al$_2$(SO$_4$)$_3$·24H$_2$O) is a well-known double salt.
Step 3: Conclusion.
Thus, the correct answer is (D) Potash alum.