Question

Which statement about ammonia is not correct? (a) Ammonia can be made by a direct reaction of the elements. (b) Aqueous solutions of ammonia are acidic. (c) Ammonia is a gas at room temperature and atmospheric pressure. (d) Ammonia is used as a reactant in the synthesis of nitric acid.

Short answer

Statement (b) is not correct.

Step-by-step solution

Understand the Characteristics of Ammonia

Ammonia (NH₃) is a compound of nitrogen and hydrogen. It is important to know that ammonia is a gas at room temperature and standard atmospheric pressure. Ammonia can also be synthesized directly from nitrogen and hydrogen through the Haber process.

Analyze Option (a)

Ammonia can indeed be made by a direct reaction between nitrogen and hydrogen, known as the Haber process. This statement is correct.

Analyze Option (b)

The aqueous solution of ammonia acts as a weak base, not an acid. Ammonia in water releases hydroxide ions (OH⁻), which makes the solution basic. Hence, this statement is incorrect.

Analyze Option (c)

Ammonia is indeed a gas at room temperature and atmospheric pressure. This statement is correct.

Analyze Option (d)

Ammonia is used as a reactant in the production of nitric acid through the Ostwald process. Therefore, this statement is correct too.

Key concepts

Haber process

The Haber process is a critical industrial method for synthesizing ammonia from nitrogen and hydrogen gases. This process takes place under specific conditions to optimize the production. - High temperatures, typically between 400°C and 500°C, are required. - Pressures of around 150-300 atmospheres.- A catalyst, usually iron with potassium hydroxide promoters, is used to accelerate the reaction. The basic chemical equation for the Haber process is:\[ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \]Here, nitrogen and hydrogen gases react to form ammonia gas. Importantly, this process is reversible, which complicates the reaction equilibrium but allows for efficient large-scale ammonia production. The Haber process not only provides a crucial source of ammonia for fertilizers but also supports numerous other applications, underscoring its industrial significance.

Ammonia properties

Ammonia is a simple compound with notable properties that allow it to be used in various applications. - **Molecular Composition**: Comprising one nitrogen atom and three hydrogen atoms (NH₃), ammonia is relatively stable.- **Physical State**: At room temperature and standard atmospheric pressure, ammonia is a gas, which is lighter than air and has a characteristic pungent smell.When dissolved in water, ammonia exhibits interesting chemical properties: - It forms a basic solution by releasing hydroxide ions, \[ NH_3 + H_2O \rightleftharpoons NH_4^+ + OH^- \]This reaction illustrates why ammonia solutions are basic rather than acidic. Consequently, aqueous ammonia is commonly used as a cleaning agent.Ammonia's chemical versatility and distinct properties make it invaluable in household and industrial settings, from cleaning products to refrigeration and fertilizers.

Ostwald process

The Ostwald process is another important industrial chemical procedure used to produce nitric acid from ammonia. Developed by Wilhelm Ostwald, this process is vital for the manufacture of fertilizers and explosives. Here's how it works: 1. **Oxidation of Ammonia**: Ammonia is mixed with air and passed over a platinum-rhodium catalyst at high temperatures, around 900°C. This forms nitric oxide (NO): \[ 4NH_3 + 5O_2 \rightarrow 4NO + 6H_2O \]2. **Formation of Nitrogen Dioxide**: Nitric oxide is further oxidized to nitrogen dioxide (NO₂): \[ 2NO + O_2 \rightarrow 2NO_2 \]3. **Absorption to Form Nitric Acid**: Nitrogen dioxide is absorbed in water, leading to the production of nitric acid (HNO₃): \[ 3NO_2 + H_2O \rightarrow 2HNO_3 + NO \]This show the complete series of reactions leading to nitric acid. The Ostwald process illustrates how interconnected and dependent chemical industries are, with ammonia serving as a precursor to many vital compounds and processes.