Question

On addition of `1 mL` solution of `10% NaCl` to `10 mL` gold sol in the presence of `0.0250 g` of starch, the coagulation is just prevented. What is the gold number of starch?
A. 25
B. `2.5`
C. `0.25`
D. `0.025`

Answer 1

Correct Answer - A
Gold number of lyophillic sol added in Mg in 10 ml gold sol with 1 ml of 10% NaCl to prevent cagulation.
`=0.025 g`
`0.025xx1000=25 Mg`