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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: ToxicIphone on April 13, 2013, 02:15:20 PM

Title: Acid Decomposition
Post by: ToxicIphone on April 13, 2013, 02:15:20 PM
Hello.

I have a question about the following acid decomposition equation:

H3PO4 -> H2O + HPO3

How does a single hydrogen bond with PO3 if the charge of PO3 is -3 and H is +1. I thought there should be 3 hydrogens bonded with it. When I asked my teacher this she said that it is because acid decomposition equations don't need to be balanced and that if you follow the idea that water is formed in decomposition then you just put the leftover elements together.

I don't understand how 1 hydrogen could possibly bond with something that has a charge of -3

Could someone please explain this a little more thoroughly than my teacher?

Thanks!
Title: Re: Acid Decomposition
Post by: Arkcon on April 13, 2013, 02:36:30 PM
You appear to be describing the thermal decomposition of pure phosphoric acid: http://en.wikipedia.org/wiki/Phosphoric_acid#Chemistry  Although the empirical formula of the result is given as HPO3, but really it is a larger complex called metaphosphoric acid, more correctly called (HPO3)n, on the order of dozens in a row.  http://en.wikipedia.org/wiki/Phosphoric_acids_and_phosphates#Polyphosphoric_acids  This substance is a solid, so its a crystal, and crystals terminate in a complex fashion.
Title: Re: Acid Decomposition
Post by: Borek on April 13, 2013, 03:37:19 PM
Quote from: ToxicIphone on April 13, 2013, 02:15:20 PM
When I asked my teacher this she said that it is because acid decomposition equations don't need to be balanced

Not only they need to be balanced, also the equation you listed IS balanced.

Quote
I don't understand how 1 hydrogen could possibly bond with something that has a charge of -3

Why do you think it has a charge of -3? Why not just PO3-?