Question

The coagulation of `10cm^(3)` of gold sol by `1 ml 10% NaCl` solution is completely prevented by addition of `0.025g` of starch to it. The gold number of starch is
A. `0.025`
B. `0.25`
C. `2.5`
D. `25`

Answer 1

Correct Answer - D
`0.25 g ` strach add in `10cm^(3)` gold sol
`:. 10 cm^(3)` "gold sol contain" = `0.25g`
`1 cm^(3)` gold sol contain = `(0.25xx10^(-3)mg)/(10) = 25`.