Q. On adding 1 mL of solution of 10% NaCl to 10mL of gold sol in the presence of 0.25g of starch, the coagulation is just prevented. The gold number of starch is
A) 0.25
B) 0.025
C) 2.5
D) 250
Explanation
(d)
Gold number is the number of milligrams of a hydrophilic colloid that will just prevent the coagulation of 10 mL of a gold sol on addition of 1 mL of 10% NaCl solution.
$\therefore$ Gold number =0.25$\times$1000=250
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.