Which out of the following solution having the same concentration will be most effective in causing coaugulation of the arsenic sulphide sol that is yellow in colour : KCl, `MgCl_(2),` or `Na_(3)PO_(4)` ?

Explanation

Arsenic sulphide `(As_(2)S_(3))` sol has a negative charge on it. To cause its coagulation or precipitation), the active ionc must be positively charged. According to Hardy-Schulze rule, greater the mahnitude of the positive charge on the ion, more will be its caugulating power. Thus `AlCl_(3)` containing `Al^(3+)` ions will be the most effective in caussing the coagulation of the sol.