Cbse class physics thermodynamics important question Essay

Brief Summary of the chapter: Thermodynamics: Science which deals with study of different forms of energy and quantitative relationship. 2. System & Surroundings: The part of universe for study is called system and remaining portion is surroundings. 3. State of system & state function: State of system is described in terms of T, P, V etc. The property which depends only on state of system not upon path is called state function egg. P, V, T, E, H, S etc. 4. Extensive & Intensive Properties: Properties which depends on quantity of matter called extensive prop. egg. Ass, volume, heat capacity, enthalpy, entropy etc. The properties which do not depends on matter present depends upon nature of substance called Intensive properties. egg. T,P, density, refractive index, viscosity, BP, pH, mole fraction etc. 5. Internal energy: The total energy with a system. I. E. U = E + En + SEC + Pep + Eek+ = or UP extensive properly. If LU > 1. 12 energy is released. 6. – OUR & U is state function and Heat (q): It I a form of energy which is exchanged between system and surrounding due to difference of temperature. Unit is Joule 0) or Calorie (1 Calorie = 4. 18 7.

First Law of Thermodynamics: It is law of conservation energy. Energy can neither be reared not destroyed, it may be converted from one from into another. Mathematically U = q + w, w = -p. V (work of expansion) U = q – p. For q = U + p. V, are not state function. 82 But U is state function. 8. Enthalpy (H): At constant volume V = O, q.v. = U So H=U+p. V,QPS H=U+P. V. 9. = H2O HI Relationship between QPS, q.v. I. E. H& U It is H = IS+ Eng. ART or QPS = q.v. + 10. Eng. ART Exothermic and Endothermic reactions: H = -Eve for exothermic and H endothermic reaction I. E. Evolution and absorption of heat.

Egg C+02 NO +02 11. CO + 393. 5 K], H = -393. 5 K (exothermic) NO – 180. 7 K], H = 180. 7 K (Endothermic) = for Enthalpy of reaction ( re): The amount of heat evolved or absorbed when the reaction is completed. 12. Standard Enthalpy of reaction ( RYO) at 1 bar pressure and specific temp. (KICK) I. E. Standard state. 13. Enthalpy of combustion ( chi), Enthalpy of formation ( if) (iii) Enthalpy of naturalization Enthalpy of solution (v) Enthalpy of atomization( ah), (vi)Enthalpy of Nomination ( ii) (vii) Enthalpy of Hydration ( (viii) Enthalpy of fusion ( wholly.

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H) Ox) Enthalpy of vaporization ( 14. Sub. H) fuss . (H) pap. H) fuss. H) (x)Enthalpy of sublimation ( He’s Law of constant heat summation: The total amount of heat change is same hither the reaction takes place in one step or in several steps. I. E. H = HI + H2O + HA 15. Bond enthalpy: It is amount of energy released when gaseous atoms combines to form one mole of bonds between them or heat absorbed when one mole of bonds between them are broken to give free gaseous atoms. Further 16. = B. E. (Reactants) – B. E. Products) Spontaneous & Non Spontaneous Processes: A process which can take place by itself is called spontaneous process. A process which can neither take place by itself or by initiation is called non Spontaneous. 17. Driving forces for spontaneous process: (I) Tendency for minimum energy state. (ii) Tendency for maximum randomness. 18. Entropy (S): It is measure of randomness or disorder of system. I. E. Entropy change ( S) = 19. Q ( rev. ) J. SKI . Mol Spontaneity in term of( S) S(total) = S(universe) = S(system) + S(surrounding) If S(total) is +eve, the process is spontaneous.

If S(total) is -eve, the process is non spontaneous. Second Law of thermodynamics: In any spontaneous process, the entropy of the universe always increases. A spontaneous process cannot be reversed. Equation) it is equal useful work I. E. – G = W(useful) = W(Max. ) If G = eve, process is 21. Gibbs free energy (G): defined as G spontaneous. = H – T. S & G = H – T. S (Gibbs Hellholes Effects of T on spontaneity of a process: G = H – T. S. (I) For endothermic process may be non spontaneous at law temp. (it) For exothermic process may be non spontaneous at high temp. And spontaneous at law temp.

Calculation of ( ergo) 24. Fog Relationship between ( ergo) & equilibrium constant (k) 25. Calculation of entropy change: RSI so (P) – so (r) ONE MARK QUESTIONS: State First Law of thermodynamics. What is a thermodynamic state function? Give enthalpy (H) of all elements in their standard state. From thermodynamic point to which system the animals and plants belong? Predict the sign of S for the following reactions. Ache(s) + CO(g) heat GO(s) + CO(g) For the reaction CLC(g) CO(g), What will be the sign of H and S? What is Gibbs Health equation? Define extensive properties.

Give relationship between H, U for a reaction in gaseous state. 85 ANSWERS FOR ONE MARK QUESTIONS Energy can neither be created nor destroyed. The energy of an isolated system is constant. U = q + w. A function whose value is independent of path. egg. P, V, E, H In standard state enthalpies of all elements is zero. Open system. S is positive (entropy increases) H: (-eve) b/c energy is released in bond formation and S: (-eve) b/c atoms combines to form molecules. N one step or several steps. G=H-T. S Properties which depends upon amount of substance called extensive properties.

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