Question

$ 0.25g $ lyophilic colloid is added to $ 100ml $ gold solution to prevent the coagulation on adding $ 1ml $ $ 10\% $ $ NaCl $ solution. What will be the gold number of lyophilic colloids?
 $ A. $ $ 250 $
 $ B. $ $ 125 $
 $ C. $ $ 25 $
 $ D. $ $ 0.25 $

Answer 1

Hint: Gold number is defined as the minimum mass of the colloid in milligram that is added to $ 10ml $ of red gold solution to protect it from the coagulation when $ 1ml $ of $ 10\% $ $ NaCl $ is added.

Complete step by step solution:
In the given it is given that $ 0.25g $ lyophilic colloid is added to $ 100ml $ gold solution to prevent the coagulation on adding $ 1ml $ $ 10\% $ $ NaCl $ solution, we have to calculate the gold number of lyophilic colloid. Now solve the question step by step,
Given, $ 0.25g $ lyophilic colloid is added to $ 100ml $ gold solution
 $ \Rightarrow $ $ 250mg $ lyophilic colloid is added to $ 100ml $ gold solution
 $ \Rightarrow $ lyophilic colloid is added to $ 1ml $ gold solution $ = \dfrac{{250}}{{100}} $
Now, lyophilic colloid added to $ 10ml $
Gold solution $ = \dfrac{{250}}{{100}} \times 10 $
Gold solution $ = 25 $
Hence, the gold number is $ 25 $ . so, the correct option is $ C. $

Additional information:
Colloidal solution: Colloidal solutions are nothing but a mixture in which the colloid particles are regularly suspended in a fluid. A colloid is a very small particle that is spread out uniformly all through another substance.
Lyophilic colloid: Lyophilic word is formed by two words “lyo” means liquid and “philic” means love. Lyophilic colloids are liquid loving colloids. For example, lyophilic colloids are sols of metals, metal hydroxide and metal sulphides.
Lyophobic colloid: Lyophobic word is formed by two words “lyo” means liquid and “phobic” means hate. Now lyophobic colloids can be defined as the liquid hating colloids. For example, lyophobic colloids are gum, gelatin and starch.

Note:
It is to be noted that more is the gold number indicates less is the protective power of lyophilic colloid since it means that amount is required more. It was first used by Richard Adolf Zsigmondy.