Catalysts

A student designs an experiment to test substances X, Y, and Z, to determine which one is a catalyst for the reaction: A + B ® C. Only one of the unknown substances is a catalyst, and the others are nonreactive with A, B, or C.

When 10 mL of A is added to 10 mL of B, the reaction takes twenty seconds. Bubbles form when the product C is created.

The student prepares three test tubes, each containing both reactants A and B. She adds unknowns X, Y, and Z to test tubes 1, 2, and 3, respectively. She then times the reaction in each test tube from the point when the unknown is added until bubbling stops.

How can the student identify the catalyst?

The test tube that stops bubbling first contains the catalyst.

Which statement best describes the amount of catalyst that remains at the end of a reaction?

The amount of catalyst is the same at the end as at the beginning of the reaction.

Lactase and carbonic anhydrase are examples of what type of substance?

enzyme

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?

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.

Which component is released from the active site of an enzyme during a chemical reaction?

substrate

If the activation energy required for a chemical reaction were reduced, what would happen to the rate of the reaction?

The rate would increase.

What must happen before a chemical reaction can begin?

The activation energy must be reached.

Photosynthesis is an example of

an endothermic reaction

Which statement best describes how a catalyst can speed up a chemical reaction?

The catalyst makes lower energy pathways available.

Which term describes an enzyme?

catalyst