Question

10 mL of 0.5 M NaCl is required to coagulate 1L of \( Sb_2S_3 \) sol in 2 hours time. The flocculating value of NaCl (in millimoles) is:

• A. 20
• B. 10
• C. 5
• D. 15
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Hint:

Flocculation value = Minimum millimoles of electrolyte required to coagulate 1 L of sol.

Answer 1

The Correct Option is C

Step 1: Understanding the Flocculation Value
The flocculating value (coagulation value) is defined as the minimum amount (in millimoles) of electrolyte required to coagulate 1 L of colloidal solution.
Step 2: Calculating Millimoles of NaCl Used
Given: - Volume of NaCl solution = 10 mL = \( 0.01 \) L
- Molarity of NaCl = 0.5 M
Using the formula: \[ \text{Millimoles} = \text{Molarity} \times \text{Volume in mL} \] \[ = 0.5 \times 10 = 5 \text{ millimoles} \] Thus, the flocculating value is 5 millimoles.
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