Question

For the coagulation of 200 mL of As2S3 solution, 10 mL of 1 M NaCl is required. What is the coagulating value (number of milli moles of solute needed for coagulation of 1 liter of solution) of NaCl.

• A. 200
• B. 100
• C. 50
• D. 25

Answer 1

Answer: (D)

25

Answer 2

10 ml of 1 M NaCl contains NaCl = 10 × 1 = 10 milli mole

200 ml of As2S3 required NaCl for the coagulation = 10 milli mole

$\therefore$ 1000 ml of As2S3 required NaCl for the coagulation = 10 × 1000/ 200 = 50 milli mole