question_answer

Value of \[x\] in potash alum,\[{{K}_{2}}S{{O}_{4}}.\,A{{l}_{x}}{{(S{{O}_{4}})}_{3}}\,.\,24{{H}_{2}}O\] is

A)  4             

B)  1

C)  2             

D)  None of these

Correct Answer: C

Solution :

Key Idea Potash alum is a double salt. Potash alum, \[{{K}_{2}}S{{O}_{4}}\,.\,A{{l}_{x}}{{(S{{O}_{4}})}_{3}}\,.\,\,24{{H}_{2}}O\](given) ions        valency +3 - 2 Therefore, \[A{{l}_{2}}{{(S{{O}_{4}})}_{3}}\] is compound of \[A{{l}^{3+}}\] and \[SO_{4}^{2-}\]. On comparing, \[x=2\] Hence, formula of potash alum is = \[{{K}_{2}}S{{O}_{4}}\,.\,\,A{{l}_{2}}{{(S{{O}_{4}})}_{3}}\,.\,24{{H}_{2}}O\]