Why are powdered substances more effective as adsorbents than their crystalline forms? They are microporous aluminosilicates with three dimensional network of silicates in which some silicon atoms are replaced by aluminium atoms giving Al-O-Si framework. Example: proteins, starch and cellulose form macromolecular colloids. Free downloadable chapter wise NCERT solutions for class 12 Science Chemistry in PDF format to help students in … Alternatively, one of the reactant molecules undergoes fragmentation on the surface of the solid catalyst producing active species which react faster. This will be therefore, more effective as adsorbent. The cleansing action of soap is due to the fact that soap molecules form micelle around the oil droplet in such a way that hydrophobic part of the stearate ions is in the oil droplet and hydrophilic part projects out of the grease droplet like the bristles. In this type of adsorption, the adsorbate and the surface of the adsorbent are bonded with strong chemical bonds. Question 5.15: Explain what is observed (b) Water in oil type: Here, oil is the dispersion medium while water is the dispersed phase. Types of emulsions: 5.5. (ii) nature of dispersed phase and It does not involve appreciable activation energy. NCERT Solutions for Class 12 Science Chemistry Chapter 5 - Biomolecules [FREE]. 5.11. Students can download the NCERT class 12 chemistry solution for each of the chapters from the links given in the table below. Nature of the adsorbent: Different gases are adsorbed to different extents by different solids at the same temperature. Also, greater the surface area of the adsorbent, more is the gas adsorbed. Ans: This phenomenon of attracting and retaining the molecules of a substance by a solid (or a liquid) on its surface resulting into a higher concentration of the molecules on the surface is known as adsorption. Solution: In heterogenous catalysis, generally the reactants are gaseous whereas catalyst is a solid. Question 5.20: What do you mean by activity and selectivity of catalysts? When oppositely charged sols are mixed in proper proportions to neutralize the charges of each other, coagulation of both the sol occurs. This complex then decomposes to give the product. Solution: The adsorption of a gas on a solid surface is an example of physical adsorption. This leads to a decrease in the entropy of the gas i.e., ∆S is negative. What are enzymes? Ans: Pt and Pd form inert electrodes, i.e., they are not attacked by the ions of the electrolyte or the products of electrolysis. 5.8. 5.15. 5.10. (iii) interaction between dispersed phase and dispersion medium? Here, the concentration of the adsorbate on the surface of the adsorbent increases. - 6. Negatively charged particles move towards the anode while, positively charged particles move to the cathode. Give one example of each. Get here NCERT Solutions for Class 12 Chemistry Chapter 5. Sol is obtained on dissolving these particles in a liquid. Ans: The powdered form of the adsorbent has greater surface area as compared to the crystalline form. How are colloids classified on the basis of Some of the medicines are effective as emulsions. Class 7 Maths NCERT Solutions Chapter 5 Lines and Angles Ex 5.2 Ex 5.2 Class 7 Maths Question 1. After studying this chapter, students will be able to describe the interfacial phenomenon and its significance; define adsorption and classify it into physical and chemical adsorption; explain mechanism of adsorption; explain the factors controlling adsorption from gases and solutions on solids; explain adsorption results on the basis of Freundlich adsorption isotherms; appreciate the role of catalysts in industry; enumerate the nature of colloidal state; describe preparation, properties, and purification of colloids; classify emulsions and describe their preparation and properties; describe the phenomenon of gel formation; list the uses of colloids. all gases may be adsorbed on the surface of a solid. The adsorption isotherm is the plot between the extent of adsorption (xm)\left ( \frac{x}{m} \right )(mx​)against the pressure of gas (P) at constant temperature (T). (a) Grease on cloth Give four examples of heterogeneous catalysis. Keep visiting BYJU’S for the latest NCERT sample papers and previous year solved questions. (v) Effect of pressure Coordination Compounds. Solution: Colloids can be classified into eight types depending upon the physical state of the dispersed phase and the dispersion medium. Soln: Common salt (a typical crystalloid in an aqueous medium) behaves as a colloid in a benzene medium. The adsorption rate of a gas on the solid surface increases with the increase in the surface area of the adsorbent. are adsorbed to a great extent in comparison to gases such as H2, O2 etc. It into smaller pieces or powdering it, is one of the chapters from the.! All the gases absorbed or adsorbed and thus, prevents the oil drop coming! When dissolved in water structure containing water molecules in the colloidal solution is left.! For boards as well as competitive exams specific in nature as well as synthesised for selectivity! 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