Answer:
1
Explanation:
I find that the easiest way to balance an equation in basic solution is first to balance as if it were in acid and then convert to base.
Your skeleton equation is
NO₂⁻ + Al ⟶ NH₃ +AlO₂⁻
1. Separate the reaction into two half-reactions
NO₂⁻ ⟶ NH₃
Al ⟶ AlO₂⁻
2. Balance all atoms other than O and H
Done
3. Balance O
NO₂⁻ ⟶ NH₃ + 2H₂O
Al + 2H₂O ⟶ AlO₂⁻
4. Balance H
NO₂⁻ + 7H⁺ ⟶ NH₃ + 2H₂O
Al + 2H₂O ⟶ AlO₂⁻+ 4H⁺
5. Balance charge
NO₂⁻ + 7H⁺ + 6e⁻ ⟶ NH₃ + 2H₂O
Al + 2H₂O ⟶ AlO₂⁻+ 4H⁺ + 3e⁻
6. Equalize electrons transferred
1×[NO₂⁻ + 7H⁺ + 6e⁻ ⟶ NH₃ + 2H₂O]
2×[Al + 2H₂O ⟶ AlO₂⁻+ 4H⁺ + 3e⁻]
7. Add the two half-reactions
1×[NO₂⁻ + 7H⁺ + 6e⁻ ⟶ NH₃ + 2H₂O]
2×[Al + 2H₂O ⟶ AlO₂⁻+ 4H⁺ + 3e⁻]
NO₂⁻ + 2Al + 2H₂O ⟶ NH₃ + 2AlO₂⁻+ H⁺
8. Convert to base
NO₂⁻ + 2Al + 2H₂O ⟶ NH₃ + 2AlO₂⁻+ H⁺
H⁺ + OH⁻ ⟶ H₂O
NO₂⁻ + 2Al + H₂O + OH⁻ ⟶ NH₃ + 2AlO₂⁻
The coefficient of OH⁻ is 1.
