Energy Changes And Rates Of Reactions Content

Question 1

Collision theory

Answer 1

A model that explains that a reaction will only proceed when reactant particles collide effectively

Question 2

Factors for an effective collision

Answer 2

1) the correct orientation

2) sufficient energy (kinetic energy equal to or greater than the activation energy)

Question 3

Bond breaking vs bond formation

Answer 3

Bond breaking is endothermic
Bond formation is exothermic

Question 4

Enthalpy change and types of rxns
(Eproducts-Ereactants)

Answer 4

1) 🔼H > 0 is endothermic

2) 🔼H < 0 is exothermic

Question 5

List the factors affecting reaction rate

Answer 5

Concentration
Pressure
Temperature
Surface area
Catalyst
Nature of reacting substances

Question 6

Concentration changes and rxn rate

Answer 6

1) more/less particles per unit volume
2) more/less collisions per unit time
3) more/less effective collisions per unit time
4) increases/decreases reaction rate

Question 7

Temperature changes and reaction rate

Answer 7

1) average kinetic energy of the particles increases/decreases

2) increase/decrease in number of particles with sufficient kinetic energy to overcome activation energy

3) increases/decrease the chance/frequency of effective collisions per unit time

4) increases/decreases reaction rate

Question 8

Pressure changes and rates of reactions

Answer 8

1) the pressure of a gas is inversely proportional to the volume (at a fixed temperature)

2) an increase/decrease in pressure therefore decreases/increases the volume of the gaseous mixture

3) this increases/decreases the concentration of all reacting gases

4) the number of gas molecules increases/decreases per unit volume

5) this results in more/less collisions per unit time

6) there are more/less effective collisions per unit time

7) increasing/decreasing the reaction rate

Question 9

Surface area changes and reaction rates

Answer 9

1) change increases/decreases the surface area of contact of the substance

2) more/less particles are exposed to the chemical reaction

3) more/less collisions per unit time

4) resulting in more/less effective collisions per second

5) hence an increased/decreased reaction rate

Question 10

Adding catalysts and reaction rate

Answer 10

1) adding a catalyst provides an alternative pathway for the reaction to happen which has a lower activation energy

2) therefore more particles have sufficient energy to start a reaction

3) hence the number of effective collisions per second increases

4) this increases the rate of the reaction