Chapter 6 Reaction Rates

Question 0

What affects the rate of a chemical reaction ?

Answer 0

• Concentration
• Pressure
• Temperature
• Catalysts
• State of Subdivision.

Question 1

Define reaction rate.

Answer 1

Reaction rate measures the speed at which reactants are consumed or products are formed in a chemical reaction.

Question 2

What are the conditions that must be met for the Collision Theory to occur?

Answer 2

• the reacting particles; atoms, molecules or ions must collide.
• the collision energy must equal or exceed a certain minimum amount known as the activation energy, Ea.
• the reacting particles must collide with a suitable orientation.

Question 3

How does the Transition state occur?

Answer 3

• When colliding particles have sufficient kinetic energy they will approach close enough (collide).
• This is also known as the Activated Complex.

Question 4

Why is the Transition state/ Activated Complex the highest potential energy state for the reaction?

Answer 4

• This is because as reacting particles approach each other, repulsive forces between their electron clouds cause them to slow down and lose kinetic energy.
• This lost kinetic energy converts to increased potential energy of the colliding particles.

Question 5

What is a Transition State?

Answer 5

• The Transition State is a point in the reaction where new bonds are forming and the original bonds are breaking.
• It is an unstable arrangement that decomposes quickly to form either the original reactants or new products.

Question 6

Define Activation Energy.

Answer 6

It is the minimum collision energy required to form the transition state is known as the activation energy Ea.

Question 7

Define Temperature.

Answer 7

Temperature is a measure of the average kinetic energy of the particles of a substance.

Question 8

As the temperature rises…

Answer 8

so does the average kinetic energy of its particles. Thus at a higher temperature the average collision energy of the particles in a reaction mixture increases.

Question 9

Why does Raising Concentration increases the reaction rate?

Answer 9

A higher concentration of reacting particles causes an increases in the rate of collisions between these particles, hence an increase in rate of reaction.

Question 10

How doe Raising the Pressure of a Gaseous reagent increases reaction rate?

Answer 10

• A higher pressure means a greater concentration of reacting gas molecules.
• This causes an increase in the rate of collisions between these molecules, hence an increase in rate of reaction.

Question 11

How does using a Catalyst increase the rate of reaction?

Answer 11

• A catalyst provides a reaction pathway with lower activation energy.
• As a result a greater percentage of collisions have collision energy equal to or greater than the activation energy.
• Thus a greater percentage of the collisions are successful and hence the rate of reaction increases.

Question 12

How does Increasing the state of sub-division (surface area) of a solid or liquid in a heterogenous reaction will increase reaction rate?

Answer 12

• Increasing the surface area exposes a greater amount of reacting particles to the possibility of a collision.
• This results in an increase rate of collision between reacting particles and hence the reaction rate increases.

Question 13

Define Heterogenous.

Answer 13

• Heterogenous reactions involve reactants that are in two separate phases, eg. solid/solid, solid/liquid, solid/gas, liquid/gas or liquid/liquid.
• In these reactions the reacting particles can only collide at the surface boundary where the separate phases make contact.