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1 Chapte Notes Subject: Chemisty Class: XI Chapte: Themodynamics Top concepts 1. The banch of science which deals with study of diffeent foms of enegy and thei inteconvesion is called themodynamics. 2. A system in themodynamics efes to that pat of univese in which obsevations ae made. 3. The emaining potion of univese which is not pat of system constitutes the suoundings. The suoundings include eveything othe than the system. 4. The wall (eal o imaginay) that sepaates the system fom the suoundings is called bounday. 5. Types of the System Types of the System Exchange of Exchange of matte enegy Open Yes Yes Closed Yes No Isolated No No 6. The state of a themodynamic system is descibed by its measuable o macoscopic (bulk) popeties. The state of the suoundings can neve be completely specified. 7. State vaiables ae the measuable popeties of system equied to descibe the state of the system. Examples ae tempeatue, pessue, volume etc. 8. Vaious types of pocesses Type of pocess Isothemal Adiabatic Isobaic Definition Pocess in which tempeatue of system emains constant Pocess in which thee is no tansfe of heat between the system and suoundings Pocess in which pessue of system

2 Isochoic emains constant Pocess in which volume of system emains constant 9. Evey substance possesses definite amount of enegy which depends on factos such as chemical natue, tempeatue and pessue etc. Intenal enegy, U of the system epesents the total enegy of the system 10. Wok done in a adiabatic pocess and sign convention Wok done (w ad ) Sign of w By the system - On the system + 11.Heat changes and sign convention Heat(q)tansfeed Fom suoundings to the system Fom system to the suoundings Sign of q Fist Law of Themodynamics: ΔU = q + w 13. Fist law of themodynamics is also called as law of consevation of enegy i.e. enegy can neithe be ceated no destoyed. It also states that the enegy of an isolated system is constant. 14.Absolute value of the intenal enegy can neve be detemined only change in intenal enegy can be detemined. 15.A pocess o change is said to be evesible, if a change is bought out in such a way that the pocess could, at any moment, be evesed by an infinitesimal change. 16.Fo an isothemal evesible pocess Vf q=- w ev nRTlog V 17.Fo isothemal ievesible change q= -w =pex Vf -Vi i 18.Expansion of a gas in vacuum (p ex = 0) is called fee expansion. No wok is done duing fee expansion of an ideal gas whethe the pocess is evesible o ievesible 19.Fo adiabatic change, q = 0 and ΔU = w ad

3 20.The of a system may be defined as the sum of the intenal enegy and the poduct of its pessue and volume. It is denoted by the symbol H and is given by H = U + PV 21.Change in ΔH = U + pδv 22.Enthalpy change and sign convention Type of eaction Definition ΔH Exothemic eactions Reactions in - which heat is evolved duing the eaction Endothemic eactions Reactions in which heat is absobed duing the eaction + 23.An extensive popety is a popety whose value depends on the quantity o size of matte pesent in the system. Examples ae mass, volume, intenal enegy,, heat capacity, etc 24.An intensive popety is a popety whose value does not depend on the quantity o size of matte pesent in the system. Examples ae tempeatue, density, pessue etc. 25.Specific heat, also called specific heat capacity is the quantity of heat equied to aise the tempeatue of one unit mass of a substance by one degee Celsius (o one Kelvin). 26.Relation between amount of heat, q, equied to aise the tempeatues of a sample, specific heat of the substance, c and change in tempeatues is given as q = mc ΔT =CΔT 27.At constant pessue as q p = Cp T = H 28. At constant volume as q V = CV T = U 29. Fo a mole of an ideal gas, Cp-C V= R 30. Caloimety is an expeimental technique that helps detemining enegy changes associated with chemical o physical pocesses 31.The change accompanying a eaction is called the eaction ( ) H H= (sum of enthalpies of poducts)- (sum of enthalpies of eactants) 32.The standad of eaction is the change fo a eaction when all the paticipating substances ae in thei standad states. The standad state of a substance at a specified tempeatue is its pue fom at pessue of 1 ba.

4 33.Diffeent types of No. Type of 1 Standad Enthalpy of fusion o Mola of fusion Definition The change that accompanies melting of one mole of a solid substance in standad state Symbol fus 2 Standad Enthalpy of vapoization o Mola of vapoization 3 Standad Enthalpy of sublimation 4 Enthalpy of fomation o Standad mola of fomation 5 Enthalpy of combustion 7 Enthalpy of atomisation 8 Bond dissociation The change that accompanies vapoizing of one mole of a liquid at constant tempeatue and unde standad pessue (1ba) The change when one mole of a solid substance sublimes at a constant tempeatue and unde standad pessue (1ba) The change fo the fomation of one mole of a compound fom its elements in thei most stable states of aggegation Enthalpy change when 1 mole of substance is completely bunt in excess of oxygen o ai Enthalpy change in beaking one mole of bonds of a substance completely into atoms in gaseous state Amount of enegy equied to beak one mole of bond of a paticula type between atoms in gaseous state vap sub f comb o c a bond θ 9 Enthalpy of Enthalpy of solution of a substance is H sol

5 solution the change when one mole of substance dissolves in a specified amount of solvent 34.A balanced chemical equation togethe with the value of its is called a themochemical equation 35.Hess s Law of Constant Heat Summation: If a eaction takes place in seveal steps then its standad eaction is the sum of the standad enthalpies of the intemediate eactions into which the oveall eaction may be divided at the same tempeatue 36. Bon-Habe Cycle is used to detemine lattice of ionic compounds since they cannot be detemined by expeiment diectly. 37.The lattice of an ionic compound is the change which occus when one mole of an ionic compound dissociates into its ions in gaseous state 38. H H H θ θ θ sol lattice hyd 39.A pocess that has natual tendency of occuence in a paticula diection and is evesible only by application of some extenal agency is known as spontaneous pocess. 40.The pocesses which ae fobidden and ae made to take place only by supplying enegy continuously fom outside the system ae called nonspontaneous pocess. 41.Entopy (S) is the measue of andomness of a system. It is a state function. 42.Entopy inceases fom solid to gas. Entopy is maximum fo gases as they have maximum disode. 43.Accoding to Second law of themodynamics entopy of the univese always inceases duing a spontaneous change 44.Fo evesible pocess entopy change is given by q ev ΔS = whee T q is heat absobed o eleased duing the eaction ev T is the tempeatue of theeaction 45. At constant pessue q ev = ΔH ΔH ΔS= T 46. Fo spontaneous pocess ΔS total =ΔS sys ΔS su 0 47.Decease in and incease in entopy of system independently cannot seve the citeia fo spontaneity

6 48.Gibbs function o Gibbs enegy is denoted by G. G=H-TS 49. The citeia fo spontaneous eaction in elation to G at constant pessue and constant tempeatue. If G < 0, pocess is spontaneous If G = 0, pocess is in equilibium If G > 0, pocess is non-spontaneous 0 50.Relation between Gibbs enegy change ( ΔG ) and equilibium 0 constant (K) ΔG =-RTlnK 51. In case of endothemic eactions of eaction ( H θ ) is lage and positive. In such a case, value of equilibium constant(k) will be much smalle than 1 and the eaction is unlikely to fom much poduct 52. In case of exothemic eactions of eaction ( negative and H θ 0 ΔG is also lage and negative. In such cases equilibium constant (K) is lage than 1 and eactions go to completion 53. Effect of tempeatue on Spontaneity of Reactions ) is