Topic 16.2: Activation energy

Question 1

Relationship between rate constant and temperature

Answer 1

k remains constant if the temperature is only constant

Question 2

Explanation of the relationship

Answer 2

As the temperature increases, the reactants possess more energy and the rate constant increases.

Question 3

Relationship between rate constant and absolute temperature.

Answer 3

k = Ae^[-Ea/RT]

Question 4

What does e^[-Ea/RT] represent in the Arrhenius equation?

Answer 4

Fraction of molecules in gas phase that have E ≥ Ea

Question 5

What does A represent in the Arrhenius equation?

Answer 5

Fraction of molecules that have the appropriate orientation to react

Question 6

What does the value of A imply about the complexity of the molecules?

Answer 6

The value of A will be smaller for reactions between more complicated molecules since these can collide in many different ways and only a small proportion of collisions will be in the correct orientation for reaction.

Question 7

Formulas based on Arrhenius equation

Answer 7

ln⁡k =-(Ea/R )(1/T) + ln⁡A

ln[k1/k2] = Ea/R (1/T2-1/T1)