Answer (i), (ii) or (iii) based on an industrial chemistry case study - Leaving Cert Chemistry - Question A - 2018

The major industrial use of magnesium oxide produced is as a refractory material. It is utilized in lining reaction vessels for steel industry and in high-temperature applications for line furnaces due to its heat-resistant properties.

The substance with a higher concentration in the seawater effluent compared to the seawater feedstock is calcium chloride (CaCl₂). This is because it is a byproduct of the chemical reactions taking place during the extraction process.

To avoid ecological damage, companies may implement various measures such as:

1. Controlling noise and dust emissions during the production process.
2. Using electrostatic precipitators to minimize air pollution.
3. Managing the temperature of wastewater before it is returned to the sea, ensuring that suspended solids and harmful substances are filtered. This is critical in maintaining the ecological balance in the surrounding marine environment.

The catalyst used in the conversion of ammonia to nitric acid is platinum and rhodium gauze (Pt & Rh). This catalyst facilitates the oxidation of ammonia efficiently, enhancing the reaction rate.

The negative ΔH value (-905.2 kJ) indicates that the reaction is highly exothermic, meaning it releases a significant amount of energy. This property is economically significant as it allows for the reaction to maintain a higher rate of productivity while minimizing energy costs for heating, thereby reducing overall operational costs for the production process.

The next two balanced equations in the production of nitric acid are:

1. The oxidation of nitrogen monoxide to nitrogen dioxide: $2NO(g) + O_2(g) → 2NO_2(g)$

2. The conversion of nitrogen dioxide to nitric acid: $3NO_2(g) + H_2O(l) → 2HNO_3(aq) + NO(g)$

Nitric acid production can negatively impact environmental quality primarily through:

1. The release of nitrogen oxides (NOx) into the atmosphere, which contribute to air pollution and the formation of acid rain.
2. The potential for leaks, resulting in ammonia and nitric oxide being harmful to aquatic and terrestrial ecosystems, leading to plant damage and corrosion.

The optimal industrial conditions for the Haber process are approximately:

• Temperature: 450 °C
• Pressure: 200 atmospheres

The hydrogen feedstock is typically obtained by the steam reforming of hydrocarbons, represented by the balanced equation: $CH_4(g) + H_2O(g) → CO(g) + 3H_2(g)$

The nitrogen feedstock is obtained from the air through a process of fractional distillation or from natural gas processing, either way allowing the separation of nitrogen gas (N₂) from other atmospheric gases.

The formation of urea from ammonia can be represented by the following balanced equation: $2NH_3 + CO_2 → NH_2CONH_2 + H_2O$