Tiêu đề DPP-7 SOLUTION.pdf ✅

CLASS : XIth SUBJECT : CHEMISTRY DATE : DPP No. : 7 1 (a) R ― COONa has hydrophilic (—COO ― ) and hydrophobic moities and thus, dispersion of C6 H6 and water is possible. 2 (a) In colloid particles, the range of diameters i.e.,particle size is of the order of 1 to 100 nm. 4 (a) Sodium dodecyl sulphate (SDS) CMC (mm)>-10 Hexadecyl trimethyl ammonium bromide (CTAB) Note At a certain concentration surfactant molecules start to aggregate and form micelle, the concentration is called critical micellisationconcentration(CMC). 5 (c) Hydrophobic sol are irreversible in nature. They have no affinity between the dispersed phase and the dispersion medium (H2O). Further once precipitated, they do not form the colloidal sol by simple addition of water. 7 (b) Sulphur sol is prepared by the oxidation of H2S by bromine. Br2 + H2S→2HBr + S sol 8 (c) When some FeCl3 is added to the Fe(OH)3 solution, Fe3+ ions are preferentially adsorbed on Fe(OH)3 particle. Thus, it turns into positive ferric hydroxide sol[Fe(OH)3 ]Fe3+. This process is called peptisation. 9 (a) Emulsion is solution of liquid in liquid. Cod liver oil is emulsion. 10 (b) Adsorbent adsorbs impurities from surface of substance. Animal charcoal is good adsorbent. The impurities adsorb on its surface and thus it decolourises colour of liquids. Topic :- SURFACE CHEMISTRY Solutions
11 (a) Flocculation value ∝ 1 Coagulating power Fe(OH)3is a positively charged sol. To coagulateFe(OH)3, negative charge electrolyte is used and greater the value of negative charge, coagulating power will be strong. Among the given electrolytes, NaCl has lowest coagulating power. So, its flocculation value will be maximum. 12 (c) Gold sol is a lyophobic sol. Gold particles have very less affinity towards dispersion medium, hence its sol can be easily coagulated. 13 (d) H + for (a) ; mixture of gases for (b) and Mn 2+ for (c) formed during reaction acts as catalyst. 14 (d) Palladium being a transition element, adsorbs the hydrogen gas to a greater extent and the molecules of H2 are held to the surface of the metal by chemical forces 15 (b) ∵ Protective power ∝ 1 gold number ∴ Order of protective power will be Gelatin > Haemoglobin > Sodium acetate (0.005) (0.05) (0.7) 16 (d) A catalyst change the activation energy of the reaction. As a result, the reaction follows an alternate path and the rate of reaction will change. 17 (d) Adsorption of a gas on a solid depends on (a)nature of the gas and solid (b)temperature (decreases with increase in temperature) (c)pressure 19 (a) Fog is a colloidal solution in which water (liquid, dispersed phase) is dispersed in air (gas, dispersion medium) 20 (c) Larger is surface area, more is efficiency of catalyst. The surface area becomes more in finely powdered state, colloidal state or if surface is rough.
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. A A A A C B B C A B Q. 11 12 13 14 15 16 17 18 19 20 A. A C D D B D D C A C