International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What is the role of a catalyst in a chemical reaction?

1. It slows down the reaction

2. It changes the reaction products

3. It speeds up the reaction without being consumed

4. It requires additional energy to function

The correct answer is: It speeds up the reaction without being consumed

A catalyst plays a critical role in chemical reactions by providing an alternative pathway for the reaction to occur, which results in a decrease in the activation energy required. This allows the reaction to proceed more quickly, thereby speeding up the overall process. Importantly, a catalyst is not consumed in the reaction. This characteristic means that it can be used repeatedly in multiple reaction cycles, which highlights its efficiency and effectiveness in promoting chemical transformations without undergoing any permanent changes itself. In contrast, the other options suggest misconceptions about catalysts. While some reactions can be slowed down when specific inhibitors are introduced, a catalyst is specifically meant to accelerate reactions. A catalyst does not alter the reaction products; instead, it facilitates the same products but at a quicker rate. Lastly, it does not require additional energy to function in a way that is distinct from other forms of energy input required for reactions; rather, it lowers the activation energy barrier, making the reaction more favorable without demanding extra energy input. Thus, the role of a catalyst is pivotal in enhancing the rate of reaction efficiently.