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1、How to predict the direction of reaction through the equilibrium constantReaction quotient(J)For a general chemical reaction,as follow:aA(g)+bB(aq)+cC(s)=xX(g)+yY(aq)+zZ(l)In any state:The criterion of reaction quotient(J)(1)J K meaning that the reaction is overdone and must be reversed.To calculate
2、 the composition of the equilibrium systemExample:Reaction:CO(g)+Cl2(g)COCl 2(g)under isothermal and isochoric conditions,known that K=1.5 108 at 373K.At the beginning,c0(CO)=0.0350molL-1,c0(Cl2)=0.0270molL-1,c0(COCl2)=0.How much are the partial pressure of various components and the equilibrium con
3、version rate of carbon monoxide when a reaction reaches equilibrium state at 373k?Solve：CO(g)+Cl2(g)COCl 2(g)Initial:cB/(molL-1)0.0350 0.0270 0Beginning:pB/kPa 108.5 83.7 0Change:pB/kPa -(83.7-x)-(83.7-x)(83.7-x)Equilibrium:pB/kPa 24.8+x x (83.7-x)K is too larger,x is very small,83.7-x 83.7 24.8+x 2
4、4.8At equilibrium:p(CO)=24.8kPa p(Cl2)=2.3 10-6 kPa p(COCl2)=83.7kPa4.3 To judge the movement of chemical equilibrium(1)The effect of concentration on chemical equilibrium(2)The effect of pressure on chemical equilibrium(3)The effect of temperature concentration on chemical equilibrium(4)The Le Chat
5、eliers law The movement of chemical equilibrium:When external conditions change,the old equilibrium state is broken,and then a new equilibrium state establish.(1)For chemical reactions involving aqueous solution,at equilibrium state,J=K.(2)When the reactant concentration increases or the product con
6、centration decreases,J K,suggesting that the equilibrium state goes in the opposite direction(left).Example:At 25 OC,the reaction occurs,as follow:Fe2+(aq)+Ag+(aq)Fe3+(aq)+Ag(s)In which,known that K =3.2。(1)when c(Ag+)=1.00 10-2 molL-1,c(Fe2+)=0.100 molL-1,c(Fe3+)=1.00 10-3 molL-1,which direction sh
7、ould a reaction goes?(2)When a reaction reaches an equilibrium state,how much are the concentrations of various reactants and products?(3)How much is the conversion rate of Ag+?(4)If the initial concentration of Ag+and Fe3+remains unchanged,when the Fe2+increases to 0.3 mol/L,how much is the convers
8、ion rate of Ag+?Solve:(1)To calculate J and then to judge the direction of reaction J K ,Reaction goes forward(2)To calculate the composition of equilibrium system Fe2+(aq)+Ag+(aq)Fe3+(aq)+Ag(s)Beginning:cB/(molL-1)0.100 1.0010-2 1.0010-3 Change:cB/(molL-1)-x -x xEquilibrium:cB/(molL-1)0.100-x 1.001
9、0-2-x 1.0010-3+xc(Ag+)=8.4 10-3molL-1 c(Fe2+)=9.84 10-2 molL-1c(Fe3+)=2.6 10-3molL-1 3.2x21.352x2.210-3=0 x=1.610-3(3)To calculate the conversion rate of Ag+?Fe2+(aq)+Ag+(aq)Fe3+(aq)+Ag(s)Equilibrium 0.300-1.0010-2 1.0010-3+cB/(molL-1)1.0010-22 (1-2)1.0010-2 2(4)Supposing that the conversion of Ag+is 2 when the reaction system reaches a new equilibrium stateThe equilibrium state goes to the right
