Question

On adding 1ml solution of 10% nacl to 10ml gold sol in presence of 0.25 g starch so that coagulation is just prevented what will be gold number of starch

Answer 1

Hey mate,

◆ Gold Number-
It's the minimum amount of starch in milligrams which prevents a colour change from red to violet of 10ml gold sol by the addition of 1 ml of 10% NaCl solution.

◆ Answer- Gold number = 250

◆ Explanation-
# Given-
0.25 g = 250 mg of starch is added to 10 ml gold solution.

# Solution-
For 10 ml gold solution, colloid required is calculated by
x = 250 × 10 / 10
x = 250 mg.

Thus gold number of given starch will be 250.

Hope that is helpful..