Chapter 4A - Collision Theory

Question 1

What do chemical reactions involve?

Answer 1

• atom rearrangement
• reactant collisions
• bonds within reactants must be broken requiring activation energy
• atoms rejoin and form new bonds as products releasing energy

Question 2

What is the collision theory?

Answer 2

Describes conditions required for chemical reactions to occur

Question 3

What are successful collisions?

Answer 3

Collisions that allow products to be formed

Question 4

What are the conditions for a chemical reaction to occur?

Answer 4

Particles must physically collide with:
* Sufficient kinetic energy
* Correct orientation for bonds to actually break

Question 5

Why must reactant particles have sufficient energy?

Answer 5

Required to break bonds within reactant particles overcoming the activation energy barrier

Question 6

Define Rate of Reaction

Answer 6

Rate of change of concentration of reactants and products over time

Question 7

What does reaction rate depend on?

Answer 7

• Frequency of collisions
• Proportion of collisions that involve energies > EA

Question 8

What are the factors affecting reaction rate?

Answer 8

• Temperature
• Surface Area
• Concentration
• Pressure

Question 9

How does Temperature affect reaction rate?

Answer 9

As temperature increases, average kinetic energy of particles & reaction rate increase because
* particles move faster, colliding more often
* Greater proportion of collisions have energy > EA (most important)

Question 10

How does Surface Area affect reaction rate?

Answer 10

• collisions occur b/w particles at the surface of solid and particles of the other reactant
• A finely divided solid has greater SA, so more particles are exposed to surface
• collisions occur more often, increasing reaction rate

Question 11

How does concentration affect reaction rate?

Answer 11

• When concentration of solution increases, there are more reactant particles in a given volume
• Collision frequency and successful collisions increases, increasing reaction rate

Question 12

How does Pressure affect reaction rate?

Answer 12

• increasing pressure increases reactant particles in a given volume
• collision frequency, and collision success increases, increasing reaction rate

Question 13

Define Open System

Answer 13

• Any gas produced in a reaction is allowed to escape
• Both matter/energy are exchanged b/w system and surroundings

Question 14

Define Closed System

Answer 14

• Any gas produced in a reaction cannot escape as the reaction vessel is airtight
• only energy (not matter) is exchanged with surroundings
• allows for possibility of reverse reactions

Question 15

What are the common reaction rate measuring techniques?

Answer 15

• Temperature Change
• Change in mass
• Precipitation formation/colour change
• Volume of gas evolved
• pH change

Question 16

Method and Type

Technique: Temperature Change

Answer 16

Use a thermometer to measure the temperature change over time for an open system
Quantitative Measurement

Question 17

Technique: Change in Mass

Answer 17

Use a balance to measure the change in mass (formation of solid or a gas in an open system) over time
Quantitative Measurement

Question 18

Technique: Precipitate Formation/ Colour Change

Answer 18

Visual observation of the production of a precipitate or colour change over time for a open system
Qualitative Measurement

Question 19

Technique: Volume of Gas Evolved

Answer 19

Use a gas syringe to measure the volume of gas produced in a closed system over time
Quantitative measurement

Question 20

Technique: pH change

Answer 20

Use an indicator or pH probe to measure the change in pH of a reaction mixture over time for an open system
Quantitative/Qualitative