Química Analítica III
Función de Gran
Alejandro Baeza1FQ UNAM Alejandro Baeza
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Reaccion de titulacion: “titrationreaction” reacción operativa
Al + 3OH = Al(OH)3(s)
In CoVo
Agr vCt
Ape CoVo-(1/3(vCt) (1/3)vCt
Reacciòn al equilibrio “intertitrationreaction”
Al + H2O = Al(OH)3(s) + 3H
Ka = (H)3/(Al3+)= 10-3pH/(CoVo-(1/3)vCt)/(Vo+v)
Re-arreglando according to Gran´s method:
10-3pH(Vo+v) = KaCoVo – (1/3)KaCt(v)17FQ UNAM Alejandro Baeza
El volumen de equivalencia
.
3CoVo =nOH
vCt =nOH=3CoVo
veq= (3CoVo)/Ct
10-3pH(Vo+v) = KaCoVo – (1/3)KaCt(v)10-3pH(Vo+v) = KaCoVo – (1/3)KaCt(v)
10-3pH(Vo+v) = KaCoVo – (1/3)KaCt((3CoVo/Ct))
10-3pH(Vo+v) = 0 10-3pH(Vo+v)
v
veq
18FQ UNAM Alejandro Baeza