For the coagulation of 200 mL of `As_(2)S_(3)` solution, 10 mL of 1 M NaCl is required. What is the coagulating value of NaCl.

Options

A. 200
B. 100
C. 50
D. 25

Explanation

To find the coagulating value of NaCl for the coagulation of 200 mL of As₂S₃ solution, we can follow these steps:

### Step 1: Understand the given data
We are given:
- Volume of As₂S₃ solution = 200 mL
- Volume of NaCl solution used = 10 mL
- Concentration of NaCl solution = 1 M

### Step 2: Calculate the amount of NaCl in millimoles
Since the concentration of NaCl is 1 M, we can calculate the number of millimoles of NaCl used:
\[ \text{Millimoles of NaCl} = \text{Volume (mL)} \times \text{Concentration (M)} = 10 \, \text{mL} \times 1 \, \text{mmol/mL} = 10 \, \text{mmol} \]

### Step 3: Relate the amount of NaCl to the volume of As₂S₃ solution
We know that 10 millimoles of NaCl are required to coagulate 200 mL of As₂S₃ solution.

### Step 4: Calculate the coagulating value of NaCl
The coagulating value is defined as the amount of electrolyte (in millimoles) required to coagulate 1 liter (1000 mL) of the colloidal solution.

To find the coagulating value of NaCl, we can set up the following proportion:
\[ \text{Coagulating value of NaCl} = \frac{\text{Millimoles of NaCl}}{\text{Volume of As₂S₃ solution in liters}} = \frac{10 \, \text{mmol}}{0.2 \, \text{L}} = 50 \, \text{mmol/L} \]

### Final Answer
The coagulating value of NaCl is **50 millimoles per liter**.

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