Ammonia gas reacts with aqueous nitric acid to form aqueous ammonium nitrate, a fertilizer. (a) Write the balanced chemical equation for the reaction, including the physical states. (b) Write the complete ionic and the net ionic equations for the reaction.
The Correct Answer and Explanation is:
(a) Balanced Chemical Equation (with physical states):
NH₃(g) + HNO₃(aq) → NH₄NO₃(aq)
(b) Complete Ionic Equation:
NH₃(g) + H⁺(aq) + NO₃⁻(aq) → NH₄⁺(aq) + NO₃⁻(aq)
Net Ionic Equation:
NH₃(g) + H⁺(aq) → NH₄⁺(aq)
Explanation (about 300 words):
The reaction between ammonia gas (NH₃) and nitric acid (HNO₃) is a classic acid-base neutralization reaction. Ammonia is a weak base, while nitric acid is a strong acid. When ammonia reacts with nitric acid, the ammonia molecule accepts a proton (H⁺) from the nitric acid to form ammonium ion (NH₄⁺). The nitrate ion (NO₃⁻) from nitric acid remains unchanged in solution and pairs with the ammonium ion to form ammonium nitrate (NH₄NO₃), which stays dissolved in water as an aqueous solution.
The balanced molecular equation shows the overall reaction: one molecule of ammonia gas reacts with one molecule of aqueous nitric acid to form one formula unit of aqueous ammonium nitrate. Including the physical states helps identify how each compound behaves in the reaction. NH₃ is a gas, HNO₃ is in aqueous solution, and NH₄NO₃ also forms an aqueous solution.
The complete ionic equation breaks all strong electrolytes (like HNO₃) into their ions. In this case, nitric acid dissociates completely into hydrogen ions (H⁺) and nitrate ions (NO₃⁻). Ammonia, being a weak base, does not dissociate in water but instead reacts directly with H⁺. The ammonium nitrate product contains NH₄⁺ and NO₃⁻ ions in solution.
The net ionic equation removes the spectator ions, which are ions that do not change during the reaction. In this reaction, NO₃⁻ appears on both sides and does not participate directly in the transformation. What remains is the actual chemical change: ammonia accepting a proton to form the ammonium ion.
This reaction is important in agriculture, as ammonium nitrate is a common nitrogen-containing fertilizer used to enhance plant growth.
