A Level Chemistry OCR Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Prepare for the A Level Chemistry OCR Exam with quizzes. Study with flashcards, multiple choice questions, hints, and explanations. Enhance your understanding and boost your confidence for success!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

What does the rate of reaction measure?

The speed at which a catalyst operates
The change in concentration of a reactant or product over time
The total energy released during a reaction
The temperature change during a reaction

The correct answer is: The change in concentration of a reactant or product over time

The rate of reaction measures the change in concentration of a reactant or product over time. This concept quantifies how quickly a chemical reaction occurs, which can be observed through the increase in concentration of products or the decrease in concentration of reactants as the reaction proceeds. This measurement is essential for understanding reaction kinetics, allowing chemists to predict how changes in conditions (such as temperature, pressure, or concentration) will affect the speed of the reaction. The other choices address different concepts related to reactions but do not define the rate of reaction itself. For instance, the speed of a catalyst relates to its effectiveness in increasing the reaction rate without being consumed, while the total energy released is a concept tied to the enthalpy change of the reaction. Temperature change is relevant in evaluating reaction conditions but does not directly measure how fast a reaction occurs.