`100mL` of a colloidal solution is completely precipitated by addition of `5mL` of `1M` `NaCl` solution. Calculate the coagulation value of `NaCl` .

Explanation

Coagulation value is the millimoles of an electrolyte that must be added to 1 L of a colloidal solution for complete coagulation.
`:. 5 mL " of 1 M NaCl" = 1/1000 xx 5 = 0.005` or 5 mmoles.
100 mL of a colloidal solution require NaCl for complete coagulation = 5 mmoles .
`:.` 1 L of colloidal solution require NaCl for complete coagulation = 50 mmoles
`:.` Coagulation value of NaCl = 50.