Balance the following redox reaction in acidic solution: H3PO4 + HNO2--> N2O4 + H3PO3
See your post above.
H3PO4 + 2 HNO2 > N2O4 + H3PO3 + H2O
To balance a redox reaction in acidic solution, follow these steps:
Step 1: Assign oxidation numbers for each element in the reaction
Start by assigning oxidation numbers to each element in the reaction. Remember that hydrogen (H) is typically +1, oxygen (O) is typically -2, and any element on its own has an oxidation number of 0.
H3PO4: H has an oxidation number of +1, P is +5, and O is -2.
HNO2: H is +1, N is +3, and O is -2.
N2O4: N is +4, and O is -2.
H3PO3: H is +1, P is +3, and O is -2.
Step 2: Identify the elements undergoing oxidation and reduction
Look for elements that change oxidation numbers between the reactants and products. In this reaction, phosphorus (P) is going from +5 to +3 (reducing its oxidation number), and nitrogen (N) is going from +3 to +4 (increasing its oxidation number).
Step 3: Balance elements undergoing oxidation and reduction
Balance the atoms undergoing oxidation and reduction by adding appropriate coefficients to the compounds. In this case, we can balance P by adding a coefficient of 2 to H3PO4 on the reactant side:
2H3PO4 + HNO2 --> N2O4 + H3PO3
Step 4: Balance atoms other than hydrogen and oxygen
Now, examine the non-hydrogen and non-oxygen atoms. In this reaction, there are only phosphorus (P), nitrogen (N), and hydrogen (H) atoms. The number of hydrogen atoms is already balanced.
To balance phosphorus, add a coefficient of 2 to H3PO3 on the product side:
2H3PO4 + HNO2 --> N2O4 + 2H3PO3
Finally, balance the nitrogen by adding a coefficient of 3 to HNO2 on the reactant side:
2H3PO4 + 3HNO2 --> N2O4 + 2H3PO3
Step 5: Balance oxygen by adding water molecules
In acidic solution, you can add water (H2O) to balance the oxygen atoms. In this reaction, we need to balance the oxygen atoms on both sides of the equation. On the product side, we have 4 oxygen atoms in N2O4, and on the reactant side, we have 13 oxygen atoms (3 in HNO2 and 10 in H3PO4).
To balance the oxygen, add 9 water molecules (H2O) to the reactant side:
2H3PO4 + 3HNO2 + 9H2O --> N2O4 + 2H3PO3
Step 6: Balance hydrogen by adding hydrogen ions (H+)
Now, balance the hydrogen atoms by adding hydrogen ions (H+) to the side that needs them. In this case, we need 18 hydrogen atoms on the product side (6 in N2O4 and 12 in H3PO3).
To balance hydrogen, add 18 hydrogen ions (H+) to the product side:
2H3PO4 + 3HNO2 + 9H2O --> N2O4 + 2H3PO3 + 18H+
Step 7: Balance the overall charge by adding electrons
Now, check the overall charge of the reaction. In this case, both sides of the equation have a net charge of 0.
This is the balanced equation for the redox reaction in acidic solution:
2H3PO4 + 3HNO2 + 9H2O --> N2O4 + 2H3PO3 + 18H+