# Question Video: Predicting Which Set of Conditions Should Have the Greatest Rate of Reaction Science

A student is investigating the rate of reaction for a certain reaction. They repeat an experiment four times, changing the conditions each time. These are shown in the diagram below. Which experiment would you predict to have the greatest rate of reaction?

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### Video Transcript

A student is investigating the rate of reaction for a certain reaction. They repeat an experiment four times, changing the conditions each time. These are shown in the diagram below. Which experiment would you predict to have the greatest rate of reaction?

Rate of reaction measures how reactant or product concentration, mass, or volume changes over time. We can think of the rate of reaction as the speed of a chemical reaction. In this question, we want to know which of the experiments has the greatest rate of reaction. In other words, in which experiment does the reaction happen the fastest. We can see that all of the experiments are performed at a different temperature and two of the experiments use a catalyst. So we need to know how temperature and the addition of a catalyst affect the rate of reaction. In order for a chemical reaction to occur, particles must collide with enough energy and the correct orientation.

A catalyst is a substance that can decrease the minimum amount of energy needed for a reaction to occur without undergoing a permanent chemical change during the reaction. As less energy is needed for the reaction to occur when a catalyst is added, the experiments where a catalyst is used should be faster or have a greater rate of reaction than the experiments that do not use a catalyst. So, we can eliminate answer choices (B) and (D).

Now, let’s consider the effect temperature will have on the rate of reaction. As the temperature increases, the particles involved in a chemical reaction gain energy and move faster. The faster the particles move, the more likely they are to collide with each other with enough energy for a reaction to occur. So the rate of reaction tends to increase with increasing temperature. Therefore, between the two experiments that use a catalyst, the experiment at 40 degrees Celsius will have a greater rate of reaction than the experiment at 20 degrees Celsius.

In conclusion, the experiment that we predict to have the greatest rate of reaction is experiment (C), as this experiment involves the use of a catalyst and is performed at the highest temperature.