Q. On addition of 1mL solution of 10% NaCl to 10mL gold solution in the presence of 0.025 g of starch, the coagulation is prevented because starch has the following gold numbers
A) 25
B) 0.025
C) 0.25
D) 2.5
Explanation
(a)
Gold number of protective colloid is
“Colloid in milligrams which when added to 10 mL of gold solution just prevents its coagulation by 1mL of 10% NaCl solution.”
$\ Protective\ power\ \propto \frac{1}{gold\ number}$
The gold number of starch is 25, because it has very low protective power.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.