The coagulation of 100 ml of a colloidal sol of gold is completely prevented by addition of 0.25 g of a substance `X' to it before adding 10 ml of 1% NaCl solution. The gold number of `X' is:
Correct answer: B. 25
- A. 0.25
- B. 25
- C. 250
- D. 2.5
Explanation
250 mg of X is present in 100 ml of colloidal sol of gold. By definition, gold no. of X is that amount of it in mg which is present in 10 ml of colloidal gold solution. Hence 19 in 10 ml, the amount of X present is 25 mg which is the gold number of X.
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