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Explain types of physical equilibrium by giving example. |
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Answer» Solution :(i) Solid-Liquid equilibrium : There is only ONE temperature (melting point) at 1 atm. (1.013 bar) at which the two phases can coexist. It there is no exchange of HEAT with the surroundings the mass of the two phases remain constant. `{:(H_2O_((s)), hArr, H_2O_((l))),("solid",hArr,"liquid"):}}` ( Conclusion : Melting point is fixed at constant pressure.) (ii) Liquid-Vapour equilibrium : At a given definite temperature the vapour pressure is constant between liquid and its vapour in close vessel. `{:(H_2O_((l)), hArr, H_2O_((g))),("liquid",hArr,"vapour"):}}` (Conclusion: Constant temperature, `p_(H_2O)` remain constant in close vessel.) (iii) Solid-Gas equilibrium : In close vessel, at constant temperature the equilibrium occur between solid and vapour. This system known sublimation. `{:(NH_4Cl_((s)) , hArr , NH_4Cl_((g))),("solid",hArr, "vapour"):}}` (Conclusion :Constant temp., in close vessel the mass of solid and vapour.) (iv) Equilibrium involving dissolution of solid in LIQUIDS : At constant temp., saturated solution of solid is dissolution of solid in liquid TYPE equilibrium and solubility remain constant. `"Solute"_"(solid)" hArr "Solute"_"(solution)"` `"Sugar"_"(solid)" hArr "Sugar"_"(solution)"` (Conclusion : Concentration of solute in solution is constant at a given temperature.) (v) Equilibrium involving dissolution of gases in liquids : "At constant temperature in closed vessel in the saturated solution of gas in liquid the equilibrium established between soluble gas in liquid and FREE gas. In a closed vessel the concentration of gas in liquid is directly proportional to the pressure of gas. `{:("Gases"_(g),hArr,"Gas"_"(aq)"),(CO_(2(g)),hArr, CO_(2(aq))):}}` (Conclusion : `"Gas"_"(aq)" // "Gas"_"(g)"` is constant at a given temperature `CO_(2(aq))//CO_(2(g))` is constant) . |
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