[xshadow]

Hi, I have a big doubt studying the aquoacid chapter of my textbook



I don't undersant the aquoacid reactivity of alkali/alkalini earth metals

For example at lesson I understand this:

Ca²⁺  in water ---->  [Ca(OH₂)]²⁺

Now is this an aquoacid??
According to the definition it might give:

[Ca(OH₂)]²⁺  + H₂O  ----> Ca(OH)₂  + 2H⁺


But I don't understand this??!

How can a "base",an alkaline earth metal release H⁺ in order to be an "hydroxide" ?!
I usually always considr Ca(OH)2 ,or NaOH in water but never this aquoacid Na(OH₂)n ,Ca(OH2) ecc

Some explanation,please??

[AWK]

Calcium cation coordinate 4-6 water molecules. Hydrated calcium cation show very, very weak acid properties.
3 and 4 charged cations are much stronger acids, eg the Ka₁ of Al(H₂O)₆³⁺ is comparable to that of acetic acid.
see eg:
http://www.mpilkington.com/Lecture_21.pdf

[xshadow]

Calcium cation coordinate 4-6 water molecules. Hydrated calcium cation show very, very weak acid properties.
3 and 4 charged cations are much stronger acids, eg the Ka₁ of Al(H₂O)₆³⁺ is comparable to that of acetic acid.
see eg:
http://www.mpilkington.com/Lecture_21.pdf

Very helpful link,thanks !!

So ,for example the aquoacid Na(H2O)n has a pka > 14
So is this the reason why usually Na+ in water is  "inert" (no protonation of  the coordinate water) ??

[AWK]

Na(H₂O)_n ⁺

Exactly.