Question

Gold number is minimum in case of
A.Gelatin
B.Egg albumin
C.Gum Arabic
D.Starch

Answer 1

Hint: At first think about the gold number and about the topic where the gold number is present so that you can get some basic idea about the question. Gold number is a term used in colloidal chemistry.

Complete step by step answer:
Gold number is defined as the amount of protective colloid which is just sufficient to prevent coagulation of $10ml$ of a standard hydro gold sol when $1ml$ of $10\% NaCl$ solution is added to it.
Some compounds have a particular range of gold numbers. More is the gold number, less is the protective power of the lyophilic solid. The amount is taken in weight in milligrams.
In the textbooks, the following table is available for us

Protective Colloid	Gold number
Gelatin	$0.005 - 0.01$
Haemoglobin	$0.03 - 0.07$
Egg albumin	$0.15 - 0.25$
Potato Starch	$20 - 25$
Gum Arabic	$0.15 - 0.25$
Dextrin	$125 - 150$

From the above table, we can say that gelatin has a minimum range of gold numbers compared to egg albumin, gum Arabic, and starch. As gelatin has a minimum gold number it has more protective power.

So the answer is A.

Additional Information:-
 The coagulation of gold sol is indicated by a color change from red to blue or purple when particle size just increases. The gold number describes the protective power of colloids.

Note:
If the gold number is more then the protective power is less for the lyophilic sols.If water is used as the dispersion medium, lyophilic sols are called hydrophilic sols. Starch, gum, gelatin, egg albumin etc. are examples of lyophilic sols. Dextrin has a high gold number so it has less protective power.