The coagulation value of $NaCl$ for a sol is defined as the concentration of $NaCl$ in the final mixture that just coagulates the sol. For a certain sol it is $50 mmol L^{- 1}$ . What volume, in mL, of $0.50 M$ $NaCl$ must be added to $100 mL$ of the sol to just cause coagulation? Give two decimals.

Numerical answer type, answer in mL, tolerance 0.05.

Answer: 11.11 mL

Let the volume of added solution be

V

mL. The final concentration is

0.50 V / (100 + V)

mol/L, which must equal

0.050

mol/L. So

0.50 V = 0.050 (100 + V)

, i.e.

0.45 V = 5.0

V = 11.11

mL.