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# Potash Alum is

(a) $K_2SO_4.Al_2(SO_4)_3.24H_2O$
(b) $K_2SO_4.Al_2(SO_4)_3.18H_2O$
(c) $(NH_4)_2SO_4.K_2SO_4.24H_2O$
(d) None of these

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A)

Answer: $K_2SO_4.Al_2(SO_4)_3.24H_2O$

Potash Alum has the chemical formula $K_2SO_4.Al_2(SO_4)_3.24H_2O$

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Alum is a series of double sulphate salts of monovalent cations and trivalent cations containing 24 molecules of water of crystallization.
If alum contains aluminium then it is named with monovalent cation.
For example: $K_2SO_4.Al_2(SO_4)_3.24H_2O$