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balance the following reactions by the redox half-reaction method H3PO3+NO3->PO43-+N2O4

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r4rob92 | (Level 1) Valedictorian

Posted May 16, 2013 at 1:14 AM via web

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balance the following reactions by the redox half-reaction method

H3PO3+NO3->PO43-+N2O4

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llltkl | College Teacher | (Level 3) Valedictorian

Posted May 16, 2013 at 2:26 AM (Answer #1)

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The reaction is:

H3PO3+NO3->PO43-+N2O4

It occurs in acid medium.

Splitting it in two half-reactions, we get

The oxidation half-reaction:  H3PO3 →PO4^3-+ 2e^-

The atom balanced oxidation half-reaction:  

H3PO3 + H2O → PO4^3- + 5H^+ + 2e^-

And the atom balanced reduction half-reaction:  

2NO3^- + 4H^+ 2e^- → N2O4 + 2H2O

Both these half-reactions are charge balanced already.

Adding these two half reactions,

H3PO3 + 2NO3^- + H2O + 4H^+ 2e^- → PO4^3- + N2O4 + 5H^+ + 2H2O + 2e^-

Cancelling equal terms from both sides, we get the balanced chemical equation for the reaction as:

H3PO3 + 2NO3^-  → PO4^3- + N2O4 + H^+ + H2O

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