Which out of the following solutions having the same concentration will be most effective in causing the coagulation of the arsenic sulphide sol which is yellowing colour: `KCl, MgCl_2, AlCl_3 or Na_3PO_4` ?

Explanation

To determine which solution will be most effective in causing the coagulation of arsenic sulfide sol (As₂S₃), we need to analyze the charge of the sol and the valency of the cations present in the given solutions. Here’s a step-by-step solution:

### Step 1: Identify the charge of arsenic sulfide sol
Arsenic sulfide (As₂S₃) is a negatively charged sol. This means that in order to coagulate it, we need a positively charged ion.

### Step 2: List the given solutions and their cations
The solutions provided are:
1. KCl → K⁺
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