The most effective coagulating agent for antimony sulphide sol is

Step-by-step solution

According to Hardy-Scheulze rule, the coagulating power of an electrolyte will be higher for ionic components having greater charges or valencies. For coagulating a sol of a particular charge, we add particles of opposite charge. Thus, to coagulate antimony sulphide sol which is negatively charged, we must add an electrolyte with a cation of higher valency. Thus, Al ₂ ( SO ₄ )₃ that has Al ³⁺ , will be most effective for coagulating antimony sulphide.