1

How to figure out if something's a Pyro by looking at its formula? The thing I know about Pyro compounds is that

Ortho acid + Ortho acid - $\ce{H2O ->}$ Pyro compound

I have no issues if I end up with the ortho acid I am quite familiar with. For example, everyone pretty knows what $\ce{H3PO4}$ is and thus if I am asked if $\ce{H4P2O7}$ is prefixed with a Pyro, I wouldn't have any trouble.

The problem comes when I deal with compounds of $\ce{As, Sb, Si}$ and I have to check if they are prefixed with a Pyro or not....

For example, take $\ce{As2O3}$. How do I know if that's a Pyro? Now take $\ce{H4As2O7}$. How do I know if that's a Pyro?

One way I think would be to check if their oxidation states comply to their occurrence states. But that is definitely not an ideal approach. So how do I go with this? Do I need to remember these ortho acids or can I go just remembering a few?

Please someone help me in this

PS: I have already checked this webpage but I couldn't find the solution to my problem in this- What do the prefixes meta, ortho, pyro mean in inorganic chemistry?

Cuckoo Beats
  • 39
  • 7
  • 2
    The rule of thumb is the compound has to be known long enough and widely enough to deserve the pyro- prefix before the prefix was stopped being used for such condensed anions. By other words, the prefix is used for historical reasons. – Poutnik Jun 18 '23 at 12:08
  • 1
    Oxides do not use pyro prefix in their names. // For acids/ anions of acids, there is not a simple general rule, you need to know historical circumstances. Memorizing those few where pyro- is used may be easier. And even then, it is not the preferred naming. // Absence of a simple rule, based on basic principles, is rather a rule than an exception in chemistry. – Poutnik Jun 18 '23 at 12:34
  • @Poutnik I didn't know this..... it's weird they still ask questions based on Pyro acids and yes my bad, an oxide is not prefixed with a Pyro – Cuckoo Beats Jun 18 '23 at 13:08
  • Pyro compounds contain $2$ central atoms (different from oxygen and hydrogen). Exemple : $\ce{H4As2O7}$ contain $2$ arsenic atoms. It can be considered as a pyro- acid. – Maurice Jun 18 '23 at 18:51
  • okay, I did not see this either, thanks @Maurice – Cuckoo Beats Jun 19 '23 at 13:51

0 Answers0