Question

The coagulation of 100ml of collidal solution of gold is completely prevented by addition of 0.25g of a substance “X” to it before addition of 10ml of 10% Nacl solution. The gold number of “X” is:–

A) 0.25
B) 25
C)250
D) 2.5
​

Answer 1

Gold Number Of a protective colloid is a minimum weight of it milligram which must be added to 10ml of a standard red gold sol so that no coagulation of the gold sol. Hence, the gold number will be 250 as it should be added 250 milligrams to prevent coagulation

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Answer 2

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◆ Gold Number-

It's the minimum amount of protective colloid 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- 25

◆ Explanation-

# Given-

0.25 mg of colloid is added to 100 ml gold solution.

# Solution-

For 10 ml gold solution, colloid required is calculated by

x = 0.25 × 10 / 100

x = 0.025 g

x = 25 mg.

Thus gold number of given lyophillic colloid will be 25

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