coagultion is the process by which the dispersed phase of a colloid is made to aggregate and thereby separtate from the continuous phase. The minimum concetration of an eletrolyte in milli-moles per litre of the electrolyte solution which required to cause the caogultion of colloidal sol is called coagution value .
therefroe higher is the coagulatings power of effective ion, smaller will be the coagultion value of the electrolyte.
`As_(2)S_(3)`sol si negatively charged. Capacity to perciopitate of a given colloid depends upon :

Options

A. `K_(2)SO_(4)`
B. `Na_(3)PO_(4)`
C. `AlCl_(3)`
D. `CaCl_(3)`

Answer

To solve the question regarding the coagulation of the negatively charged colloidal sol \( \text{As}_2\text{S}_3 \), we need to understand the factors that influence the coagulation process. Here’s a step-by-step breakdown:

### Step 1: Understand the Concept of Coagulation
Coagulation is the process where the dispersed phase of a colloid aggregates and separates from the continuous phase. The effectiveness of coagulation depends on the charge of the particles involved.

**Hint:** Coagulation involves the aggregation of particles and is influenced by the charge of the particles.

### Step 2: Identify the Charge of the Colloid
In this case, \( \text{As}_2\text{S}_3 \) is a negatively charged colloid. To coagulate a negatively charged colloid, we need positively charged ions (cations).

**Hint:** The charge of the colloid determines the type of ions needed for coagulation.

### Step 3: Determine the Required Cations
The cations that can be used for coagulating the negatively charged \( \text{As}_2\text{S}_3 \) include:
- \( \text{K}^+ \) (Potassium)
- \( \text{Na}^+ \) (Sodium)
- \( \text{Al}^{3+} \) (Aluminium)
- \( \text{Ca}^{2+} \) (Calcium)

**Hint:** Identify the cations that can neutralize the negative charge of the colloid.

### Step 4: Compare the Charge of Cations
The coagulating power of an electrolyte is higher when the charge of the cation is greater. Among the given cations:
- \( \text{K}^+ \) has a charge of +1
- \( \text{Na}^+ \) has a charge of +1
- \( \text{Ca}^{2+} \) has a charge of +2
- \( \text{Al}^{3+} \) has a charge of +3

**Hint:** The higher the charge of the cation, the more effective it will be in coagulating the colloid.

### Step 5: Identify the Most Effective Coagulant
Among the cations listed, \( \text{Al}^{3+} \) has the highest charge (+3), making it the most effective for coagulating the negatively charged \( \text{As}_2\text{S}_3 \) sol.

**Hint:** Look for the cation with the highest positive charge for maximum coagulation efficiency.

### Conclusion
Therefore, the capacity to precipitate the negatively charged \( \text{As}_2\text{S}_3 \) colloid depends on the presence of positively charged ions, with \( \text{Al}^{3+} \) being the most effective coagulant due to its higher charge.

**Final Answer:** The capacity to precipitate \( \text{As}_2\text{S}_3 \) sol depends upon the presence of \( \text{Al}^{3+} \) ions.