The equation for the reaction between ammonia and oxygen is shown - AQA - A-Level Chemistry - Question 3 - 2018 - Paper 1

To find the Gibbs free energy change (ΔG), we use the formula:

$ΔG = ΔH - TΔS$

Where:

• ΔH = -905 kJ mol⁻¹ (given)
• T = 600 °C = 873 K (convert to Kelvin)
• ΔS = 181 J K⁻¹ mol⁻¹ × (1 kJ / 1000 J) = 0.181 kJ K⁻¹ mol⁻¹

Now substituting values:

$ΔG = -905 - (873 imes 0.181)$

Calculating:

$ΔG = -905 - 158.453 = -1063.453 ext{ kJ mol}^{-1}$

Thus,

$ΔG ≈ -1063.5 ext{ kJ mol}^{-1}$

As the temperature increases, the term $TΔS$ in the Gibbs free energy equation becomes larger, meaning that the value of $ΔG$ becomes more negative. A more negative value of $ΔG$ indicates a more favorable reaction, potentially leading to an increased reaction rate or extent.

1. Adsorption: Reactants (NH₃ and O₂) are absorbed onto the active sites of the platinum catalyst surface.
2. Reaction: The catalyst provides an alternative pathway with lower activation energy, allowing the reaction to occur more readily.
3. Desorption: Products (NO and H₂O) are released from the catalyst surface, freeing the active sites for further reactions.

In NH₃, nitrogen has an oxidation state of -3. In NO, nitrogen has an oxidation state of +2. Therefore, the change in oxidation state is:

$ΔOxidation~State = +2 - (-3) = +5$

This indicates an increase in oxidation state by 5.

The equation for the production of nitrous oxide (N₂O) from ammonia and oxygen is: