Chemical Reaction Rates: Factors, Catalysts, and Energy Changes

What is the rate of a reaction?

How fast a chemical reaction occurs.

What does collision theory state?

Particles must collide to react.

What 3 things are required for a successful collision?

Particles must collide, must have enough energy (activation energy), must have correct orientation.

Does every collision cause a reaction?

No, all 3 conditions must be met.

How does surface area affect reaction rate?

Larger surface area = faster reaction (more collisions).

How does concentration affect reaction rate?

Higher concentration = faster reaction (more particles → more collisions).

How does temperature affect reaction rate?

Higher temperature = faster reaction (particles move faster).

How does pressure affect reaction rate (gases)?

Higher pressure = faster reaction (particles closer together).

What does kinetic theory say about temperature?

Higher temperature → particles move faster → more collisions.

What is a catalyst?

A substance that speeds up a reaction without being used up.

What is an inhibitor?

A substance that slows down a reaction.

Are catalysts reactants?

No, they are not used up.

What are enzymes?

Biological catalysts.

What happens to energy when bonds break?

Energy is required (absorbed).

What happens to energy when bonds form?

Energy is released.

What is an exothermic reaction?

A reaction that releases energy.

In exothermic reactions, which is greater: breaking or forming bonds?

Energy released from forming bonds > energy needed to break bonds.

What is an endothermic reaction?

A reaction that absorbs energy.

In endothermic reactions, which is greater: breaking or forming bonds?

Energy needed to break bonds > energy released from forming bonds.

Example of synthesis reaction?

4Fe + 3O₂ → 2Fe₂O₃.

Example of single replacement reaction?

Zn + 2HCl → ZnCl₂ + H₂.

Example of decomposition reaction?

2H₂O₂ → 2H₂O + O₂.

Will a reaction with a larger surface area or smaller surface area react faster?

Larger surface area → faster reaction (more collisions).

Powdered solid vs. solid chunk — which reacts faster?

Powdered solid (more surface area exposed).

High concentration vs. low concentration — which reacts faster?

High concentration (more particles → more collisions).

Hot water vs. cold water — which reaction is faster?

Hot water (particles move faster).

High pressure vs. low pressure (gases) — which reacts faster?

High pressure (particles closer together).

Reaction with catalyst vs. without catalyst — which is faster?

With catalyst.

Reaction with correct orientation vs. incorrect orientation — which reacts?

Only correct orientation leads to reaction.

Collision with low energy vs. high energy — which reacts?

High energy (must reach activation energy).

Why does crushing a solid speed up a reaction?

Increases surface area → more collisions.

Why do reactions speed up at higher temperatures?

Particles move faster → collide more often and harder.

Why does increasing concentration speed up reactions?

More particles in same space → more collisions.

Why does a catalyst speed up a reaction?

Lowers activation energy.