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ankara55t · Jul 9, 2009, 03:36 PM

Is this right ?

2FeBr2+ 2H3PO4 --------(arrow) 2Fe(PO4)2 + 2HBr2

Perito · Jul 9, 2009, 05:06 PM

Originally Posted by ankara55t

Is this right ?

2FeBr2+ 2H3PO4 --------(arrow) 2Fe(PO4)2 + 2HBr2

No. It's not right.

You need to Google the formulas of the compounds that you are using.

Note how the ionization takes place (center section). This can help you figure out how to balance the equation. Make sure the charge is balanced (same number of + as -). Note that hydrogen bromide is HBr. You will see an equal number of H+ and Br- in the middle section.

$3 FeBr_2+ 2H_3PO_4 \,\rightleftharpoons\, 3Fe^{+2} + 6Br^- + 6H^+ + 2PO_4^{-3} \,\rightarrow\, Fe_3(PO_4)_2 + 6HBr$

You didn't ask but there is also Iron(III) bromide: $FeBr_3$ . That can also undergo a similar reaction:

$FeBr_3+ H_3PO_4 \,\rightleftharpoons\, Fe^{+3} + 3Br^- + 3H^+ + PO_4^{-3} \,\rightarrow\, FePO_4 + 3HBr$

Unknown008 · Jul 10, 2009, 11:13 AM

Is that possible to write charges as 'sign' then 'number'? It's the first time I see that Perito... :confused:

Well, the thing to note here is that PO4 has a valency of 3, and not two. You can deduce that (if you didn't know) from the fact that Phosphoric acid has three atoms of hydrogen in one molecule. I'm convinced that if you had seen that, the reaction would have been good. :)

Perito · Jul 10, 2009, 11:49 AM

Originally Posted by Unknown008

Is that possible to write charges as 'sign' then 'number'? It's the first time I see that Perito... :confused:

You mean like $SO_4^{-2}$ instead of $SO_4^{2-}$ ?

When I was in school, we would write it the first way (on the left) with the sign first followed by a number. I've also seen it written the second way, but I don't do it that way.

I'm convinced that if you had seen that, the reaction would have been good.

... but for the $HBr_2$

Unknown008 · Jul 10, 2009, 11:51 AM

Oh? OK, Perito. Here, we always write sulfate as $SO_4 ^{2-}$

Thanks! :)