A researcher is designing a laboratory experiment to determine whether the inorganic substance A affects the rate of a reaction between two colored liquids, X and Y. When the reaction is complete, the liquid is clear. The reaction between X and Y is similar to one used by manufacturers to produce certain chemicals in factories.Which method would best answer his question about reaction rate and what will he find out about substance A?
Answer
A
First, he should measure the final temperature of the liquid when X and Y react without substance A. Then, he should measure the final temperature when he adds substance A to X and Y. He will find out if substance A is a catalyst.
B
First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is a catalyst.
C
First, he should measure the final temperature of the liquid when X and Y react without substance A. Then, he should measure the final temperature when he adds substance A to X and Y. He will find out if substance A is an enzyme.
D
First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is an enzyme.
Explanation
Reaction rate can be compared by measuring how long the reaction takes under the same conditions, using the liquid becoming clear as the endpoint. Compare the time for X and Y alone with the time when substance A is added; a shorter time means A speeds up the reaction. This tests whether A acts as a catalyst, which speeds a reaction without being used up. Measuring final temperature does not directly measure the reaction rate, and an inorganic substance is not an enzyme.
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