Answer:
2HNO₃ + 3H₃PO₃ ⟶ 2NO + 3H₃PO₄ + H₂O
Explanation:
HNO₃ + H₃PO₃ ⟶ NO + H₃PO₄ + H₂O
One way is to balance this equation is the oxidation number method.
Step 1. Calculate the oxidation number of every atom:
H⁺¹N⁺⁵O₃⁻² + H₃⁺¹P⁺³O₃⁻² ⟶ N⁺²O⁻² + H₃⁺¹P⁺⁵O₄⁻² + H₂⁺¹O⁻²
Step 2. Identify the changes in oxidation number:
N: +5 ⟶ +2; Change = -3
P: +3 ⟶ +5; Change = +2
Step 3. Equalize the changes in oxidation number.
You need 3 atoms of P for every 2 atoms of N. This gives us total changes of +6 and -6.
Step 4. Insert coefficients to get these numbers.
2HNO₃ + 3H₃PO₃ ⟶ 2NO + 3H₃PO₄ + H₂O
Step 5. Balance O.
We have fixed 15 O on the left and 14 O on the right. We need 1 more O on the right. Put a 1 in front of H₂O.
2HNO₃ + 3H₃PO₃ ⟶ 2NO + 3H₃PO₄ + 1H₂O
Every formula now has a coefficient. The equation should be balanced.
Step 6. Check that all atoms balance.
Atom Left-hand side Right-hand side
H 11 11
N 2 2
O 15 15
P 3 3
All atoms balance.
The balanced equation is
2HNO₃ + 3H₃PO₃ ⟶ 2NO + 3H₃PO₄ + H₂O
