Chemistry Reaction Rates

Which one of the following is NOT a key concept of the collision theory:

• particles must collide in order to react

• particles must move slowly when they collide, otherwise they simply “bounce off” one another

• particles must collide with the proper orientation

• particles must collide with sufficient energy to reach the activated complex in order to react

Which one of the following factors does not affect the rate of a chemical reaction:

• humidity

• concentration

• temperature

• nature of the reactants

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NGSS.HS-PS1-5

Activation energy is the amount of energy required to

• break the bonds between the reacting molecules

• convert the reactants into the activated complex

• make the reacting particles collide

• form the bonds between the product molecules

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NGSS.HS-PS1-4

The rate of a chemical reaction normally

• increases as temperature decreases.

• decreases when a catalyst is added.

• increases as reactant concentration increases.

• decreases as reactant concentration increases.

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NGSS.HS-PS1-5

Crushing a solid into a powder will increase reaction rate because:

• the particles will collide with more energy

• the orientation of colliding particles will be improved

• the activation energy barrier will be lowered

• the powdered form has more surface area

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NGSS.HS-PS1-5

The heat of reaction, ΔH, for the forward reaction is

• +200 kJ C.

• - 50 kJ

• +150 kJ

• + 50 kJ

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NGSS.HS-PS1-4

NGSS.HS-PS3-1

The activation energy, Ea, for the reverse reaction is

• + 50 kJ

• + 200 kJ

• -150 kJ

• + 150 kJ

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NGSS.HS-PS1-4

A lump of ignited charcoal which is glowing in air burns more vigorously when lowered into a bottle of pure oxygen. This is due to an increase in

• surface area

• temperature

• concentration

• volume

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NGSS.HS-PS1-5

What happens to a catalyst in a reaction?

• It remains unchanged.

• It is incorporated into the reactants.

• It is incorporated into the products.

• It evaporates.

It is generally believed that catalysts increase reaction rates by:

• removing the activation energy barrier

• providing an alternate activation energy barrier that is lower than the original barrier

• lowering the activation energy barrier

• giving the reacting particles more energy, thus there will be more successful collisions

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NGSS.HS-PS1-5