Which Acid Has a Lower pH: HBrO4 or HIO3?

[bomba923]

Which is stronger (lower pH): $${\text{HBrO}}_{\text{4}}$$ or $${\text{HIO}}_{\text{3}}$$ ?

How would I name $${\text{HIO}}_{\text{4}}$$-- Periodic acid, I suppose?

If perchoric acid is $${\text{HClO}}_{\text{4}}$$, why then is periodic (per-iodic) acid $${\text{H}}_{\text{5}} {\text{IO}}_{\text{6}}$$ ? ( as on http://chemistry.about.com/cs/molecules/a/blperacid.htm )

Why does http://chemistry.about.com/cs/molecules/a/blperacid.htm and http://www.gfschemicals.com/chemicals/gfschem-74.asp say that periodic acid is $${\text{H}}_{\text{5}} {\text{IO}}_{\text{6}}$$ , but http://www.online-medical-dictionary.org/?q=Periodic+Acid+(HIO4) and http://www.catalogue.fisher.co.uk/scripts/search.dll?ViewMSDS&SheetNumber=19510 say that periodic acid is $${\text{HIO}}_{\text{4}}$$ ?

(I suppose $${\text{HIO}}_{\text{4}}$$ is metaperiodic acid, then?)

Finally, (it will be strong, no doubt, but) just how strong exactly would $${\text{HIO}}_{\text{4}}$$ be? (Safety Description (please)--cannot locate on web)

 

[dextercioby]

For the terminology question,i think IUPAC gave clear rules...Look for them.

Daniel.

 

[DrMark]

Which is stronger (lower pH): $${\text{HBrO}}_{\text{4}}$$ or $${\text{HIO}}_{\text{3}}$$ ?

How would I name $${\text{HIO}}_{\text{4}}$$-- Periodic acid, I suppose?

If perchoric acid is $${\text{HClO}}_{\text{4}}$$, why then is periodic (per-iodic) acid $${\text{H}}_{\text{5}} {\text{IO}}_{\text{6}}$$ ? ( as on [/QUOTE] Did you mean or [tex] {...e not the number of water molecules involved.

 

[bomba923]

Did you mean or $${\text{HIO}}_{\text{3}}$$ or $${\text{HIO}}_{\text{4}}$$

No--Actually, I wanted to see which would be most significant. The iodine with the oxygens in $${\text{HIO}}_{\text{3}}$$ greatly shifts electron density away from the hydrogen.
In $${\text{HBrO}}_{\text{4}}$$, the same thing happens. However, we have a lighter halide with few electrons---but more oxygen attached to it!

Basically, what is more important: mass of the halide (molar mass, atomic number (more electrons means more electron density away from acidic hydrogen))...or, the number of oxygen attached to the halide?

Bromine is lighter than iodine, but has one more oxygen attached to it. In a test of acid strength, which would win: $${\text{HIO}}_{\text{3}}$$ or $${\text{HBrO}}_{\text{4}}$$ ?

(But as for my other question, IUPAC says periodic acid is $${\text{HIO}}_{\text{4}}$$ , but many websites seem to differ tho...)

 

[DrMark]

No--Actually, I wanted to see which would be most significant. The iodine with the oxygens in $${\text{HIO}}_{\text{3}}$$ greatly shifts electron density away from the hydrogen.
In $${\text{HBrO}}_{\text{4}}$$, the same thing happens. However, we have a lighter halide with few electrons---but more oxygen attached to it!

Basically, what is more important: mass of the halide (molar mass, atomic number (more electrons means more electron density away from acidic hydrogen))...or, the number of oxygen attached to the halide?

Bromine is lighter than iodine, but has one more oxygen attached to it. In a test of acid strength, which would win: $${\text{HIO}}_{\text{3}}$$ or $${\text{HBrO}}_{\text{4}}$$ ?

(But as for my other question, IUPAC says periodic acid is $${\text{HIO}}_{\text{4}}$$ , but many websites seem to differ tho...)

Actually H₅IO₆ should be written as HIO₄^.2H₂O.
The pKa of HBrO₃ is -1.0 while that of HIO₃ is .74 so yes HBrO₄ is likely the stronger acid (couldn't find numbers on HBrO₄). HBrO₄ is in higher oxidation state (the halide that is) and has greater electronegativity, hence it should be the stronger acid.

 

[bomba923]

Well--I finally found my answer on:
http://wps.prenhall.com/wps/media/o...Assets/Chapter19/Text_Images/FG19_12-03UN.JPG

Now, $$HIO_4$$ will be a strong acid
But will paraperiodic a strong acid as well? (I suppose so given that one acidic hydrogen, but not quite sure)

 

[dextercioby]

Paraperiodic being $H_{5}IO_{6}$ ? Highly unlikely.U need to compare the first acidity constant of both acids (actually,monoprotic acids have only one).

Daniel.

 

[bomba923]

Yes--Paraperiodic acid is a weak polyprotic acid

But one more question tho:
In the context of naming chemicals, what do the prefixes "meta-" and "para-" indicate?

 

[dextercioby]

I think/hope it's clear for organic substances...(look for "benzene cycle").

As for inorganic,well,i'll let someone else more knowledgeable do the talking.

Daniel.