Question

Gold number gives an indication of:
A. Protective nature of colloids
B. Purity of gold in suspension
C. The charge on a colloidal solution of gold
D. g-mole of gold per litre

Answer 1

Hint:In order to the question, first we have to know about the gold number. For what gold number is known for. Then also know the property of the gold number that is an indication for colloids.

Complete answer:The gold number is the number of milligrams of the protective colloid which prevent the coagulation of $10ml$ of red gold solution when $1ml$ of a 10 percent solution of sodium chloride is added to it. Gold Number is a term used in colloidal chemistry. It is defined as the base measure of defensive colloid in milligrams which forestalls a shading change from red to violet of $10ml$ gold sol by the expansion of $1ml$ of 10 percent $NaCl$ arrangement. Coagulation of gold sol is demonstrated by shading change from red to blue/purple when molecule size just increments.Coagulation occurs when the positively and negatively charged colloid particles come together and form a bigger molecule. Just like the blood cells come together to form a clot. The colloid which is added is a lyophilic colloid i.e. water-loving colloid.

Hence the correct option is (A).

Note:Gelatin is considered as the best protective colloid because the value of gold number for it is the smallest i.e. 0.001. If the gold sol is coagulated then it can be determined by the colour that is from red to blue and the size of the particle also increases.