Catalysts Answers

1

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What must happen before a chemical reaction can begin?

A

The activation energy must be exceeded.

B

The activation energy must be reached.

C

The concentrations of products and reactants must be equal.

D

The concentration of reactant molecules must be reduced.

2

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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?

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.

3

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

A

More catalyst is present at the end than at the beginning of the reaction.

B

Less catalyst is present at the end than at the beginning of the reaction.

C

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

D

The catalyst is consumed by the reaction, so none remains at the end of the reaction.

4

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

A

reactant

B

product

C

substrate

D

protein

5

Which term describes an enzyme?

A

substrate

B

reactant

C

catalyst

D

product

6

The lock-and-key mechanism refers to

A

the complementary shapes of an enzyme and a substrate.

B

the attractive forces between an enzyme and a substrate.

C

the ability of an enzyme to lower the activation energy of a reaction.

D

the ability of an enzyme to “unlock” the products of a reaction.

7

Which is the best definition of activation energy?

A

the energy required to end a chemical reaction

B

the energy required to bind a substrate to an active site

C

the energy required to form or break the bonds of reactant molecules

D

the energy required to re-form bonds in product molecules

8

What is a substrate?

A

a molecule that acts as a catalyst

B

a place on the enzyme where the reaction occurs

C

a place on the product where the enzyme fits

D

a reactant that is catalyzed by an enzyme

9

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

A

substrate

B

reactant

C

product

D

enzyme

10

Which statement correctly describes a chemical reaction?

A

Reactants come out of a reaction.

B

Energy is always released.

C

Bonds between atoms break and reform.

D

Products go into a reaction.

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