This question is about ammonia.
(a) Nitrogen reacts with hydrogen to form ammonia in an industrial process.
\(N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)\)
(i) Name this industrial process.
(ii) State the meaning of the symbol \(\rightleftharpoons \).
(iii) State the conditions used in this industrial process. Include units.
(iv) Name the catalyst used in this industrial process.
(v) If the pressure is increased, the yield of ammonia increases.
Explain why, in terms of equilibrium.
(vi) If the temperature is increased, the rate of reaction increases.
Explain why, in terms of particles.
(b) Ammonia reacts with sulfuric acid to make a compound which is used as a fertiliser.
Write the chemical equation for the reaction between ammonia and sulfuric acid.
▶️ Answer/Explanation
(a) (i) The process is called the Haber process, used industrially to produce ammonia.
(ii) The symbol \(\rightleftharpoons\) means the reaction is reversible (can proceed in both directions).
(iii) Conditions:
– Temperature: 450 °C (high enough for rate, low enough for yield).
– Pressure: 200 atm (high pressure favors ammonia formation).
(iv) The catalyst used is iron (Fe), which speeds up the reaction without being consumed.
(v) Increasing pressure shifts equilibrium to the side with fewer gas molecules (right side: 2 moles of \(NH_3\) vs. 4 moles of \(N_2 + H_2\)), increasing ammonia yield.
(vi) Higher temperature increases particle kinetic energy, leading to more frequent and successful collisions (exceeding activation energy).
(b) The reaction is: \(2NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4\). Ammonium sulfate (\((NH_4)_2SO_4\)) is the fertiliser formed.
This question is about ammonia.
(a) When ammonia gas reacts with hydrogen chloride gas, white fumes of ammonium chloride are formed.
NH3 + HCl → NH4Cl
(i) What type of chemical reaction is this?
Draw a circle around the correct answer.
decomposition neutralization oxidation reduction
(ii) Watch-glasses of aqueous ammonia and concentrated hydrochloric acid were placed near each other on a table.
At first no white fumes were seen.
After a short time, white fumes were seen between the watch-glasses.
Explain these observations using the kinetic particle model.
(b) Ammonia is used in the manufacture of fertilizers.
Name the three elements present in most fertilizers which improve plant growth.
(c) Aqueous ammonia can be used to test for aluminum ions and zinc ions.
Complete the table to show the expected observations.
▶️ Answer/Explanation
(a)(i) The reaction is neutralization because ammonia (a base) reacts with hydrogen chloride (an acid) to form a salt (ammonium chloride).
(a)(ii) Using the kinetic particle model:
1. Evaporation: Molecules of NH3 and HCl escape from their liquid surfaces.
2. Diffusion: The gas molecules move randomly and collide, spreading from high to low concentration.
3. Reaction: When NH3 and HCl molecules collide, they react to form white NH4Cl fumes.
(b) The three essential fertilizer elements are:
1. Nitrogen (N) – Promotes leaf growth.
2. Phosphorus (P) – Supports root development.
3. Potassium (K) – Enhances overall plant health.
(c) Expected observations:
– Aluminum ions (Al³⁺): White precipitate, insoluble in excess ammonia.
– Zinc ions (Zn²⁺): White precipitate, dissolves in excess ammonia to form a colorless solution.
