The coagulation of `200 mL` of a positive colloid took place when `0.73 g HCl` was added to it without changing the volume much. The flocculation value of `HCl` for the colloid is
a. `36.5` , b. `100` , c. `200` , d. `150`

Options

A. `100`
B. `36.5`
C. `0.365`
D. `150`

Answer

A

Explanation

Flocculation value is minimum millimoles of electrolyte to be added to one litre of colloidal solution to cause its coagulation
`m_(HCl)= (0.73g)/(36gmol^(-1)) = 0.02mol es`
`=0.02xx10^(3)m mol es = 20 m mol es`.
`0.2L` of colloidal solution is ppt by `20m` moles.
`1L` of colloidal solution is ppt `= (20)/(0.2L) = 100` milli moles.