Fireworks contain a range of chemicals including a fuel, oxidising agents and metal salts - Scottish Highers Chemistry - Question 2 - 2022

1. Calculate moles of KClO₃:

$\text{Moles} = \frac{\text{mass}}{\text{GFM}} = \frac{4.6 g}{122.6 g/mol} \approx 0.0375 mol$

2. Using the stoichiometry from the equation:

For 2 moles of KClO₃, 3 moles of O₂ are produced. Therefore, for 0.0375 moles:

$\text{Moles of } O_2 = \frac{3}{2} \times 0.0375 = 0.05625 mol$

3. Calculate the volume of O₂ produced:

$\text{Volume} = \text{moles} \times 24 L/mol = 0.05625 mol \times 24 L/mol = 1.35 L$

Adding a catalyst has no effect on the enthalpy change of the reaction. A catalyst lowers the activation energy but does not change the inherent energy difference between reactants and products.

1. Determine moles of KClO₄:

$\text{Moles} = \frac{5.5 g}{138.6 g/mol} \approx 0.0397 mol$

2. Energy released per mole:

$\text{Energy per mole} = \frac{103 kJ}{0.0397 mol} \approx 2595.6 kJ/mol$

Increasing temperature provides particles with more kinetic energy, which increases the frequency of collisions between reactant molecules. With more energy, a greater proportion of these collisions have the required energy to overcome the activation energy barrier, leading to a higher reaction rate.

Based on the wavelength associated with peak B, which typically falls in the range, the metal responsible could be Sodium.