CBSE Class 12 Chemistry Notes: Surface Chemistry – Frequently asked Questions

Q.26 What do you mean by a catalytic promoter?

Ans. A substance, if present along with the catalyst and enhances the activity of the catalyst, it is called as a catalytic promoter. Example molybdenum for iron catalyst.

Q27 What do you mean by an emulsifier?

Ans. The emulsion formed by simply mixing pure liquids are not stable to get a stable emulsion small amount of certain other substances are added in emulsion. These substances are called emulsifiers or emulsifying agent. Example gum, agar.

Q.28 How can the constants K, and n of the freundlich adsorption equation can be calculated.

Ans. According to freundlich equation (x/m) = PK1/n
Therefore log (x/m) = log K + 1/n log P. Thus on plotting log x/m versus log P. We will get a straight line. Whose slop = 1/n and intercept on y axis = log K. Thus measuring slope and intercept n and k can be calculated.

Q.29 In case of chemisorptions why adsorption first increases and then decreases?

Ans. The initial increase in adsorption is due to the fact that heat supplied acts as the activation energy. The decreases in adsorption afterwards is due to the exothermic nature of adsorption equilibrium.

Q.30 How can a colloidal solution and true solution of same colour can be distinguished from each other?

Ans. If the solution are to be taken in a glass or beaker and light is faccused on them. The colloidal solution will scatter light due to tyndall effect and path of light becomes visible but no scattering of light occurs in the case of true solution and hence its path is b visible.

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