question_answer

Which out of the following solutions having the same concentration will be most effective in causing the coagulation of the arsenic sulphide sol that is yellow in colour: \[KCl,\,MgC{{l}_{2}},\,AlC{{l}_{3}}\] or \[N{{a}_{3}}P{{O}_{4}}\]?

Answer:

                Arsenic sulphide \[(A{{s}_{2}}{{S}_{3}})\] sol has a negative charge on it. To cause its coagulation or precepitation, the active ions must be positively charged. According to Hardy-SchuIze rule, greater the magnitude of the positive charge on the ion, more will be its coagulating power. Thus, \[AlC{{l}_{3}}\] containing \[A{{l}^{3+}}\] ions will be the most effective in causing the coagulation of the sol.