Question
Chemistry Question on Surface Chemistry
On addition of one mL solution of 10% NaCl to 10 mL 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
Answer
25
Explanation
Solution
The g number is defined as the number of milligrams of protective colloid in dry state which when added to 10 ml of Gold prevents the gold solution from coagulation on addition of 1 ml of 10% NaCl solution. Gold number of different lyophillic colloids are different. Lesser is the gold number greater is the protective power. Solution to the given problem: 1 ml of 10 % NaCl = number of milligrams of starch => 0.025 gm => 0.025?1000 = 25 mg so answer is = 25