2KClO$_3$(s) → 2KCl(s) + 3O$_2$(g) The importance of the catalyst in the reaction above is that

Analysis of the Question

The question asks for the specific role of a catalyst in the thermal decomposition of potassium trioxochlorate(V) ($KClO_3$). In this reaction, manganese(IV) oxide ($MnO_2$) is typically added as a catalyst.

Explanation of the Concept

A catalyst is a substance that increases the rate of a chemical reaction without itself being consumed in the process. It achieves this by providing an alternative reaction pathway with a lower activation energy.

• Activation Energy: This is the minimum amount of energy required for reactant particles to collide effectively and form products.
• Effect of Catalyst: By lowering the activation energy, more reactant molecules possess sufficient energy to react at a given temperature. Consequently, the reaction proceeds much faster than it would without the catalyst.

Step-by-Step Solution

1. Examine the reaction: $2KClO_3(s) \rightarrow 2KCl(s) + 3O_2(g)$ is a thermal decomposition reaction. Normally, this reaction requires very high temperatures to break the bonds in $KClO_3$.
2. Role of $MnO_2$: When $MnO_2$ is added, it acts as a catalyst. It does not change the amount of oxygen produced (that is determined by the stoichiometry of the equation), nor does it make the reaction "controllable" in the sense of safety.
3. Impact on Temperature: Because the catalyst lowers the activation energy, the reaction can occur at a significantly lower temperature than would be required if the catalyst were absent. This makes the process more efficient and safer to manage in a laboratory setting.
4. Evaluate Options: • A: Heating is still required; the catalyst just makes it easier. • B: While it helps, the primary scientific definition of the catalyst's role here is the speed and energy requirement. • C: The quantity of oxygen is determined by the moles of $KClO_3$ used, not the catalyst. • D: This correctly describes the kinetic effect of the catalyst: it speeds up the reaction at a lower temperature than would otherwise be needed.

Conclusion

The catalyst allows the decomposition to occur at a faster rate at a lower temperature, saving energy and reducing the risk associated with extreme heating.

Exam Tip

Whenever you see a question about a catalyst, look for keywords like "lowers activation energy" or "increases reaction rate." Remember: a catalyst never changes the yield (amount) of the product; it only changes how fast you get there!