# Acid Questions

1. Apr 13, 2005

### 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)

Last edited: Apr 13, 2005
2. Apr 13, 2005

### dextercioby

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

Daniel.

3. Apr 14, 2005

### DrMark

4. Apr 14, 2005

### bomba923

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...)

5. Apr 14, 2005

### DrMark

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.

6. Apr 28, 2005

### bomba923

7. Apr 28, 2005

### 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.

8. Apr 28, 2005

### 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?

Last edited: Apr 28, 2005
9. Apr 28, 2005

### 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.