Question 1

According to collision theory, which of the following is NOT a requirement for a successful chemical reaction between two molecules?

Accepted Answer

The molecules must collide with a catalyst present.

Question 2

Which of the following best explains why increasing the temperature increases the rate of a chemical reaction?

Accepted Answer

It increases the average kinetic energy of the particles, so more particles have energy greater than the activation energy ($$E_a).$$

Question 3

A powdered solid reacts much faster with a liquid than a single large chunk of the same solid. This is primarily because:

Accepted Answer

The powdered solid has a greater surface area, increasing the frequency of collisions.

Question 4

Which of the following statements about catalysts is TRUE?

Accepted Answer

A catalyst provides an alternative reaction pathway with a lower activation energy ($$E_a).$$

Question 5

The Maxwell-Boltzmann distribution curve shifts to the right and flattens as temperature increases. What does the area under the curve to the right of the activation energy ($$E_a) $$represent?

Accepted Answer

The number of particles with energy equal to or greater than $$E_a$$, which can react.

Question 6

Which of the following changes will NOT increase the rate of a reaction between a solid and a gas?

Accepted Answer

Decreasing the concentration of the gas.

Question 7

A flour mill explosion is a real-world example of which factor affecting reaction rate?

Accepted Answer

Increasing surface area by dispersing flour dust in the air.

Question 8

Which of the following best describes the effect of a catalyst on a reaction energy profile?

Accepted Answer

It lowers the activation energy 'hump' between reactants and products.

Question 9

In a decomposition reaction, why does doubling the concentration of the reactant typically double the reaction rate?

Accepted Answer

Because more particles are present to collide and react at any time.

Question 10

Which of the following is the best explanation for why not all collisions between reactant molecules result in a chemical reaction?

Accepted Answer

Some collisions do not have the correct orientation or sufficient energy to overcome the activation energy barrier.

Question 11

A reaction between two gases is found to proceed much faster at higher concentrations. This is best explained by:

Accepted Answer

Higher concentration increases the frequency of collisions per second.

Question 12

Which of the following is TRUE about the effect of temperature on the Maxwell-Boltzmann distribution?

Accepted Answer

Increasing temperature increases the number of particles with energy equal to or greater than the activation energy.

Question 13

Which of the following scenarios would NOT increase the rate of a reaction between a solid and a liquid?

Accepted Answer

Decreasing the surface area of the solid.

Question 14

Which of the following is a correct statement about enzymes?

Accepted Answer

Enzymes are biological catalysts that speed up reactions without being used up.

Question 15

A reaction has an activation energy ($$E_a) of$$ $$50\ \mathrm{kJ/mol}. If a $$catalyst lowers the activation energy to $$30\ \mathrm{kJ/mol}$$, what is the most likely effect on the reaction rate?

Accepted Answer

The reaction rate will increase because more particles have energy greater than $$E_a.$$

Question 16

Which of the following best describes why a catalyst does not appear in the overall chemical equation for a reaction?

Accepted Answer

A catalyst is regenerated at the end of the reaction and is not consumed.

Question 17

In a reaction between a metal and an acid, which of the following changes would most likely increase the rate of hydrogen gas production?

Accepted Answer

Grinding the metal into smaller pieces to increase surface area.

Question 18

Which of the following is the best explanation for why flour dust in air can cause an explosion in a grain silo?

Accepted Answer

The flour dust increases the surface area available for reaction with oxygen, leading to a rapid reaction.

Question 19

Which of the following is TRUE about the effect of increasing concentration on reaction rate for a two-particle collision reaction?

Accepted Answer

Increasing concentration increases the frequency of collisions, leading to a faster reaction rate.

Question 20

Which of the following is a correct statement about the energy profile of an exothermic reaction?

Accepted Answer

The reactants must overcome an activation energy barrier before forming products.

Chemical Kinetics: Collision Theory and Factors Affecting Reaction Rates

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