Write a balanced equation for the proton transfer reaction between hydrofluoric acid (HF) and ammonia (NH₃). Identify each conjugate acid-base pair, and rewrite the equilibrium arrows to indicate if the forward or reverse reaction is favored.

Verified step by step guidance

1. Start by writing the unbalanced chemical equation for the reaction between hydrofluoric acid (HF) and ammonia (NH₃). HF is the acid, and NH₃ is the base. The reaction involves the transfer of a proton (H⁺) from HF to NH₃, forming fluoride ion (F⁻) and ammonium ion (NH₄⁺): $HF\; +\; NH₃\; \to \; F⁻\; +\; NH₄⁺$.
2. Balance the equation. Since the reaction already has one molecule of each reactant and product, the equation is balanced as written: $HF\; +\; NH₃\; \rightleftharpoons \; F⁻\; +\; NH₄⁺$.
3. Identify the conjugate acid-base pairs. HF (acid) donates a proton to form F⁻ (its conjugate base), and NH₃ (base) accepts a proton to form NH₄⁺ (its conjugate acid). The pairs are: HF/F⁻ and NH₃/NH₄⁺.
4. Determine the direction of the equilibrium. Compare the relative strengths of the acids and bases. HF is a weak acid, and NH₄⁺ is a weaker acid than HF. Similarly, NH₃ is a weak base, and F⁻ is a weaker base than NH₃. This means the forward reaction is slightly favored, but the equilibrium lies close to the middle.
5. Rewrite the equation with equilibrium arrows to reflect the favorability of the forward reaction: $HF\; +\; NH₃\; \rightleftharpoons \; F⁻\; +\; NH₄⁺$. The double arrows indicate that the reaction is reversible, with the forward reaction being slightly favored.

Key Concepts

Proton Transfer Reaction

A proton transfer reaction, also known as an acid-base reaction, involves the transfer of a proton (H⁺) from an acid to a base. In this context, hydrofluoric acid (HF) acts as the acid, donating a proton, while ammonia (NH₃) serves as the base, accepting the proton. Understanding this concept is crucial for writing the balanced equation and identifying the conjugate acid-base pairs.

Conjugate Acid-Base Pairs

Conjugate acid-base pairs consist of two species that differ by the presence of a proton. In the reaction between HF and NH₃, HF donates a proton to form its conjugate base, fluoride ion (F⁻), while NH₃ accepts the proton to form its conjugate acid, ammonium ion (NH₄⁺). Identifying these pairs is essential for understanding the dynamics of the reaction and the equilibrium established.

Equilibrium Arrows

Equilibrium arrows (↔) indicate that a reaction can proceed in both the forward and reverse directions, establishing a dynamic balance between reactants and products. In this case, the direction favored can be determined by factors such as the strength of the acids and bases involved. Understanding how to rewrite these arrows based on the reaction's favorability is key to accurately representing the chemical behavior of HF and NH₃.