[WESIDA]

ok, well i tried to google a page where i can find out the strength of acids and their relativity to the perodic table, but i wasn't lucky in doing so. like for Example if you go down the peridoic table which acid would be stronger? HF or HCl. what about left to right?
and also is IC>OUS acids
thanks

[Mitch]

pKa Values for a bunch of acids can be found in the menu to your left.

[AWK]

From HF, HCl, HBr and HI the strongest is the last one. Try to explain this fact in category of radius of halogen

[WESIDA]

cool, so if you go down the peridictable that kind of determines the strength of acids, and i will take alook at the pka values
thanks  

[shelanachium]

For oxy-acids Pauling's Rules are a good guide. Take the anion obtained by removing one proton e.g [HSO4]- for sulphuric acid. This is [HOSO3]-, the charge is distributed over 3 oxygen atoms. in [ClO]- from HOCl it is confined to one O atom, in [H2PO4]- which is [(HO)2PO2]- the charge is spread over two. Then:

If charge on anion confined to one O atom pK = about 8 to 10 (HOCl, H3BO3,H6TeO6 - loss of H+ gives an anion with charge confined to one O atom, any others have H attached as OH group so carry no charge)

Charge over 2 O atoms: pK = 2 -5 (HNO2, most organic acids RCO2H, H5IO6, H3PO3 which is thus shown not to ionise to (HO)2PO- but HOPHO2- with one H attached to P.

Charge over 3 atoms: pK -4 to -7: HNO3, H2SO4, sulfonic acids RSO3H, HClO3

Charge over 4 atoms: pK -10 or stronger: HClO4.

The rule even works for N atoms in cyano-compounds (whose triply-bonded N is as electronegative as O) thus HC(CN)3 is like HNO3 and HC5(CN)5 which rejoices in the name of pentacyanocyclopentadiene is superacidic (charge of anion spread over 5 N atoms).

The rules make sense because an anion in which the charge is widely dispersed will attract protons less, and the corresponding acid will be stronger.