A 42.12 %(w/v) solution of NaCl causes precipitation of a certain sol in 10 hours. The coagulating value of NaCl for the sol is

$\text{ [Given: Molar mass : }\mathrm{Na}=23.0\mathrm{g}{\mathrm{mol}}^{-1};\mathrm{Cl}=35.5\mathrm{g}{\mathrm{mol}}^{-1}\text{ ] }$

$coagulation value =\frac{millimoles of electrolyte}{volume of solution in L}$

$Molarity of NaCl =\frac{\%(w/v)x10}{M.Wt}$

$Molarity of NaCl =\frac{42.12x10}{58.5}=7.2M$

$Millimoles of NaCl electrolyte=7200$

$Coagulation value for 10 hours=\frac{Millimoles of electrolyte}{Volume of solution in L}=7200$

$For 2 hours coagulation value =\frac{7200x2}{10}=1440 millimoles/L$