Kinetics: Collision Theory and Energy

A reaction is most likely to occur when reactant particles collide with

• both proper energy and proper orientation

• proper orientation, only

• proper energy, only

• neither proper energy nor proper orientation

In each of the four beakers shown below, a 2.0-centimeter strip of magnesium ribbon reacts with 100 milliliters of HCl(aq) under the conditions shown. In which beaker will the reaction occur at the slowest rate?

• A

• B

• C

• D

Which statement explains why the speed of some chemical reactions is increased when the concentration of the reactant is increased?

• The activation energy of the reaction is decreased.

• The density of the reactant particles increases.

• There are more reactant particles which results in more collisions

• The speed of the reactants increases.

If the pressure on gaseous reactants increases, the reaction rate will

• decrease as the number of collisions decreases

• decrease as the number of collisions increases

• increase as the number of collisions decreases

• increase as the number of collisions increases

Which statement describes characteristics of an endothermic reaction?

• The sign of ΔH is negative and the products have more potential energy than the reactants.

• The sign of ΔH is positive and the products have less potential energy than the reactants.

• The sign of ΔH is positive and the products have more potential energy than the reactants.

• The sign of ΔH is negative and the products have less potential energy than the reactants.

Which mathematical expression represents the forward activation energy for a chemical reaction?

• (the potential energy of the activated complex) − (the potential energy of the products)

• (the potential energy of the activated complex) − (the potential energy of the reactants)

• (the heat of fusion) − (the heat of vaporization)

• (the potential energy of the products) − (the potential energy of the reactants)

Use the potential energy diagram and the chemical equation to answer the following question. The reverse reaction can be best described as an

• endothermic reaction in which energy absorbed

• exothermic reaction in which energy is released

• exothermic reaction in which energy is absorbed

• endothermic reaction in which energy is released

Refer to the potential energy diagram showing regions labeled (1) through (4). Which region corresponds to the enthalpy change (ΔH) for the reaction from reactants at A to products at B?

• Region (2) from A up to the peak

• Region (1) along the baseline distance

• Region (4) vertical difference between A and B

• Region (3) from peak down to valley

In the same diagram, which region represents the activation energy for the forward reaction?

• Region (4) net difference between A and B

• Region (3) energy drop after the peak

• Region (2) energy rise from A to peak

• Region (1) horizontal reaction progress

When a catalyst is added, which labeled regions change value while reactants A and products B remain the same?

• Region (3) only

• Regions (2) and (3) only

• Region (2) only

• Regions (1) and (4) only