Chemie pH-Wert?
Kann mir jemand bei der Berechnung des pH-Wertes helfen?
a) Ameisensäure (0,01mol/l) ; pKS= 3,65
b) Bromwasserstoffsäure (0,02mol/l) ( starke säure glaube ich?)
c)Natriumacetat (0,1mol/l)
d) Kaliumfluorid (0,25mol/l) ; pKB= 11
e)Natriumhydrogensulfat (0,5mol/l)
bei b) Bromwasserstoffsäure habe ich -log (0,02) = 1,698
den rest weiss ich nicht wie ich das berechnen soll.. Bei schwachen und starken Säuren gibt es nämlich verschiedene Rechenwege
There are a total of two relevant formulas for pH calculation, once in the case of strong acids which virtually completely dissociate, and once in the case of weak acids in which there is hardly any dissociation. We skip the pH formula for medium-strong acids.
With strong acids, the pH is calculated by
because you can start from a complete dissociation.
With weak acids, you expect
It should be noted that in the case of corresponding bases, you must first calculate the pOH value to weak acids (e.g. in the case of acetate) above the pKB value before you are then using the relationship
pH + pOH = 14
to pH.
Formic acid is also a relatively weak acid… how do I get worth the KS? That would be 10^14-3,65 so KS= 10^10,35
The pKS value is sufficient for the pH calculation. But if you want to determine the Ks value from the pKs, you expect
KS = 10^-pK