Writing Net Ionic Equations

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superrad
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Joined: Sun Oct 07, 2012 8:57 pm

Writing Net Ionic Equations

Post by superrad »

"Consider the reaction when aqueous solutions of ammonium iodide and potassium phosphate are combined." Then I need to write the net ionic equation.

When I try to write down the equation I get it as:
NH4I+KH2PO4=(NH4)3PO4+KI

Which is apparently an impossible reaction. What am I doing wrong?
GrahamKemp
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Joined: Mon Mar 19, 2012 10:12 pm

Re: Writing Net Ionic Equations

Post by GrahamKemp »

First, determine which potassium phosphate you're dealing with. Monopotassium dihydrogen phosphate, Dipotassium hydrogen phosphate, or Tripostassium phosphate?

Second, just swap the potassium atoms with an equal number of ammonium groups.
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Ammonium iodide + Monopotassium dihydrogen phosphate = Ammonium dihydrogen phosphate + Potassium iodide.

NH4I + KH2PO4 = (NH4)H2PO4 + KI

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Ammonium iodide + Dipotassium hydrogen phosphate = Diammonium hydrogen phosphate + Potassium iodide.

2 NH4I + K2HPO4 = (NH4)2HPO4 + 2 KI

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Ammonium iodide + Tripotassium phosphate = Triammonium phosphate + Potassium iodide.

3 NH4I + K3PO4 = (NH4)3PO4 +3 KI
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