Question

The gold number of gelatin is `0.01` . Calculate the amount of gelatin to be added to `1000mL` of a colloidal sol of gold to prevent its coagulation, before adding `1mL` of `10%NaCl` solution.
A. 2
B. 1
C. 4
D. 5

Answer 1

Correct Answer - B
Gold number of gelatin `=0.01`
or `0.01mg` gelatin required to be added to `10mL` of gold sol to completely prevent coagulation of `1mL` of `10%NaCl` solution.
Therefore gelatin added to `1000mL` of gold sol to
prevent coagulation `=(0.01xx1000)/(10)=1mg` .