InorganicChemistry英文PPT (19).ppt

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1、The calculation of weak monoprotonic acid or base Supposing that:Concentration of HA is c0,its ionization degree is,X is an equilibrium concentration of H+HA =H+A-eq concentration:c0-X X XWhen:Ka/cacid 104 or 10,the multi-step ionizations of the solution can be generally considered that H+mainly com

2、es from the first ionization of weak acids,others should be ignored.Example:Calculated H+,H2CO3,HCO3-,CO32-,OH-,pH in the 0.01 mol/L H2CO3 solution.Ka1(H2CO3)=4.210-7,Ka2(HCO3)=4.710-11Solve：Ka1(H2CO3)/Ka2(HCO3)103H+mainly comes from the first ionization of weak acidH2CO3(aq)H+(aq)+HCO3(aq)eq con.:0

3、.10-xxxKa1(H2CO3)=c(H+)c(H2CO3)c(HCO3)=4.210-7x=6.5 10-5c(H+)=c(HCO3)=6.5 10-5 mol/L c(H2CO3)=0.10HCO3(aq)H+(aq)+CO32(aq)Eq.con.:6.5 10-5-y6.5 10-5+yyKa2(HCO3)=c(H+)c(HCO3)c(CO32)=4.710-116.5 10-5 y=6.5 10-5 6.5 10-5+y=6.5 10-5 y=Ka2 =5 4.710-11Kw=c(H+)c(OH-)=1.010-14CO32-mainly comes from the second ionizationc(OH-)=1.510-10 mol/L pH=-lgc(H+)=4.19