A chemical equilibrium: A reversible chemical reaction is at equilibrium under certaln conditions: D正=D逝≠0 The basic features of chemical equilibrium: (1)the composition of an equilibrium mixture undergoes no further change with time. (2)chemical equilibria are dynamic. (3)the equilibrium composition is independent of the path of approach
A chemical equilibrium ： υ 正 = υ 逆 ≠ 0 A reversible chemical reaction is at equilibrium under certain conditions: The basic features of chemical equilibrium ： (1) the composition of an equilibrium mixture undergoes no further change with time. (2) chemical equilibria are dynamic. (3) the equilibrium composition is independent of the path of approach
4.1.2 The standard equilibrium constant expression Equilibria involving gases H2(g)+I2(g)=2HI(g) [p(HⅡ)/pe]2 K8= p=100kpa [p(H2)1pe][p(L2)/pe] *Equilibria in aqueous solution: Sn2*(aq)+2Fe3(aq)=Sn4+(aq)+2Fe2*(aq) ke [c(Sn "le)ll c(Fe)2 [c(Sn 2+/c )]Ic(Fe 3+/ce)]2 c=1 mol.I-1
4.1.2 The standard equilibrium constant expression ☆Equilibria in aqueous solution ： H (g) I (g) 2HI(g) 2 + 2 ☆Equilibria involving gases ： Sn2+(aq)+2Fe3+(aq) Sn4+ (aq)+2Fe2+(aq) [ ( H ) / ][ ( I ) / ] [ (HI ) / ] 2 2 2 p p p p p p K = p Θ = 100kpa 2 3 2 4 2 2 [ (Sn )][ (Fe )] [ (Sn )][ (Fe )] c /c c /c c /c c /c + + + + K = c Θ = 1 mol.l-1
For a more general chemical reaction: aA(g)+bB(aq)+cC(s)-xX(g)+yY(aq)+zZ(l) exp)p p=100kpa [p(A)!pe]a[c(B)!c c=1 mol.I-1 *The value of a constant ke depends on temperature and is independent of concen- trations and partial pressures of the reaction components.Kis a dimensionless quantity(无量纲，google) The form of a standard equilibrium constant expression depends on exactly how a stoichio- metric chemical equation is written. le
For a more general chemical reaction ： aA(g) + bB(aq)+ cC(s) xX(g) + yY(aq)+ zZ(l) K [ ( ) ] [ ( ) ] [ ] ( ) [ ] ( ) b c c a p p y c c x p p A / B / X / Y / = ∗The value of a constant depends on temperature and is independent of concentrations and partial pressures of the reaction components. K ∗The form of a standard equilibrium constant expression depends on exactly how a stoichiometric chemical equation is written. KΘ is a dimensionless quantity (无量纲,google) p Θ = 100kpa c Θ = 1 mol.l-1
H2(g)+I2(g)=2HI(g) [p(H)/po12 [p(H2)/pe][p(I2)1pe] H2(g+号12(g)=H(g) K囹 2 [p(HI)/pel ()!p)( 2HI(g)=H2(g)+I2(g) L2(H)( [p(HI)/pe]
H (g) I (g) 2HI(g) 2 + 2 [ (H ) / ][ (I ) / ] [ (HI) / ] 2 2 2 p p p p p p = 2 I 2 (g) HI(g) 21 H (g) 21 + ( )1/2 = = 1/ 2 2 1/ 2 2 [ (H )/ ] [ (I )/ ] [ (HI)/ ] p p p p p p 2HI(g) (g) H (g) I 2 2 + =( )-1 [ (H ) / ][ (I ) / ] [ (HI) / ] 2 2 2 p p p p p p = K1 K1 K3 K3 K1 K2 K1 K2
The principle of multiple equilibria Example:Equilibrium constants for the following reactions have been determined: ①BrC1(g)=1/2C12(g+1/2Br2(g)K,=0.67 ②I2(g+Br2(g)=2IBr(g)K是0.051 Using this information,calculate the standard equilibrium constant for the following reaction: 32BrCI(g)+12(g)-2IBr(g)+Cl2(g)K Answer:①x2+②=③ 2BrCI(g)+L2(g)=2IBr(g)+Cl2(g) =(K)2k9=0.672×0.051=0.023
Example：Equilibrium constants for the following reactions have been determined: The principle of multiple equilibria Answer：①x2 + ② = ③ ② K 2 I2(g)+Br2(g) 2IBr(g) = 0.051 Using this information, calculate the standard equilibrium constant for the following reaction: ①BrCl(g) 1/2Cl2(g)+1/2Br2(g) K1Θ= 0.67 2BrCl (g)+ I2(g) 2IBr(g)+ Cl2(g) ③2BrCl (g)+ I2(g) 2IBr(g)+ Cl2(g) K3 = · = 0.67 K3 K1 K2 2×0.051=0.023 2 ( )