4.1.2 The standard equilibrium constant expression Equilibria involving gases H2(g+I2(g)=2HΠ(g) K- [p(HⅡ)/po]2 p=100kpa p(H2)/pe][p(I2)/pe] Equilibria in aqueous solution: Sn2+(aq)+2Fe3(aq)-Sn4+(aq)+2Fe2*(aq) ko_[c(Snce )Ic(Fe2c)2 [c(Sn2+c )]Ic(Fe3+c)]2 c=1 mol.l-14.1.2 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  = 100kpa 2 3 2 4 2 2 [ (Sn )][ (Fe )] [ (Sn )][ (Fe )] c /c c /c c /c c /c + + + + K = c  = 1 mol.l-1