Fog is a colloidal solution of
Important Points to Remember in Chapter -1 - Surface Chemistry from Embibe Experts Achieve CUET (UG) Chemistry Practice Book Solutions
(i) Adsorption is the phenomenon of attracting and retaining the molecules of a substance on the surface of a solid resulting into a higher concentration on the surface than in the bulk.
(ii) Adsorbent: The substance on the surface which adsorption takes place.
(iii) Adsorbate: The substance which is present in higher concentration at the surface of adsorbent.
(iv) Physisorption is the type of adsorption in which adsorbate is held on the surface of adsorbent by van dar Waal’s forces.
(v) Chemisorption is the type of adsorption in which adsorbate is held on the surface of adsorbent by chemical bonds.
(vi) Enthalpy of Adsorption: Enthalpy change accompanying the adsorbate. It is always negative.
(vii) Extent of Adsorption decreases with increase in temperature and increases with increase in pressure.
(viii) Adsorption Isotherm: A relationship between extent of adsorption vs. pressure at constant temperature.
(ix) Freundlich Adsorption Isotherm:
2. Catalysts:
(i) Substances, which accelerate the rate of a chemical reaction and themselves remain chemically and quantitatively unchanged after the reaction, are known as catalysts.
(ii) When the reactants and the catalyst are in the same phase, the process is said to be homogeneous catalysis.
(iii) The catalytic process in which the reactants and the catalyst are in different phases is known as heterogeneous catalysis.
3. Colloidal State:
(i) A state in which the particle size of the substance is in the range .
(ii) Sol: A colloidal solution containing solid as the disperse phase and liquid as the dispersion medium.
(iii) Lyophilic Sol: A colloidal solution in which there is greater affinity between the disperse phase and the dispersion medium.
(iv) Lyophobic Sol: A colloidal solution in which there is little affinity between the disperse phase and the dispersion medium. Lyphobic sols are less stable.
(v) Multimolecular Colloid: A colloid in which colloidal particles are clusters or aggregates of smaller molecules.
(vi) Macromolecular Colloid: A colloid in which colloidal particles are macromolecules.
(vii) Associated Colloid: A colloid which is formed when concentration of the solute exceeds a limit.
(viii) Peptization: It is the process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte (peptizing agent).
(ix) Coagulation: Precipitation of a colloidal solution by induced aggregation of colloidal particles.
(x) Coagulation value: Minimum concentration of the electrolyte in millimoles per litre needed to cause coagulation of the sol.
(xi) Hardy-Shultze Rules: In case of electrolytes, the ion carrying charge opposite to that of colloidal particles is effective in causing coagulation. Greater the valency of the ion causing the coagulation greater is the coagulating power.
(xii) Brownian Movement: The zig-zag movement of colloidal particles.
(xiii) Tyndall Effect: Scattering of light by colloidal particles.
(xiv) Electrophoresis: The movement of colloidal particles towards one of the electrodes on passage of electricity through colloidal solution.
(xv) Gold Number: A parameter used for expressing protective power of a lyophilic colloid.
