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I'm having trouble finding out the salt formation equation for $\ce{(NH4)2C2O4}$

I thought it was $\ce{NH3 + H2C2O4}$ but that doesn't seem to balance out.

$\ce{HC2O4-}$ seems to work, but are ions allowed in salt formation/neutralization formulas?

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$\ce{2 NH3 + H2C2O4}$ - the reaction won't balance itself - you have to do it by putting stoichiometric coefficient.

On the other hand ammonium hydrogen oxalate - (NH4)HC2O4 also exists.

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Where am I wrong? First of all, note that the ammonia is dissolved in water. So there is an ion that's involved in the reaction, not the ammonia itself. And second, the charge of the ion involved requires a different coefficient for ammonia. Notice that the $\ce{H+}$ cations in Hydrogen oxalate are spectator ions.

The formation of Ammonium Oxalate will be a precipitation reaction. (Or some may put it an acid-base one) Answer these in order to reach a final net ionic reaction:

  1. What are the ions that are present in the final product (ammonium oxalate)?

The ions involved are ammonium ($\ce{NH4+}$) and oxalate ($\ce{C2O4^{2-}}$).

  1. Notice the charges of those ions:

Ammonium has a 1+ charge (that's written correctly as +, but of course, I wanted to emphasize) and oxalate has a 2-.

  1. The other ions are spectator ions. These two ions actually form the precipitate. But the final formula (where your misunderstanding rises from) is

$\ce{(NH4)2C2O4}$

You can now write the net ionic equation and get it balanced.

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  • $\begingroup$ How come in the case of $\ce{(NH4)2SO4}$ the reaction goes like $\ce{2NH3 + H2SO4-}$ --> $\ce{(NH4)2SO4}$? $\endgroup$ – quidproquo Feb 27 '15 at 16:51
  • $\begingroup$ @quidproquo Sulfuric acid doesn't have a negative charge. And, ammonia is aqueous in water, thus ammonium is what that's participating in the reaction. $\endgroup$ – M.A.R. Feb 27 '15 at 16:54
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$\Huge{\mathrm{(NH_4)_{\color{red}{2}}C_2O_4}}$

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  • $\begingroup$ It's really hard to tell what OP misses. Probably the whole concept of ionic compounds. I gave it another shot. Hopefully it'll work for them. $\endgroup$ – M.A.R. Feb 27 '15 at 16:16
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I finally remembered that ammonium salts come from ammonia and does not produce water. I had trouble balancing because I thought water was part of the products. $$\ce{2NH3 + H2C2O4 -> (NH4)2C2O4}$$

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