The Arrhenius Equation

Question 1

HOW does temperature affect the rate of reaction?

Answer 1

• increase KE, increases collisions
• increases number of collisions that have energy greater than E_a
  
  • shape of Maxwell-Boltzman distribution curve

Question 2

What is the fraction of molecules with energy greater than the activation energy given by?

Answer 2

• e^-E_a/RT
• R = gas constant
• T = temp.

Question 3

What is the Arrhenius equation?

Answer 3

• links E_a to the rate constant
• k = A e^-E_a/RT
  
  • K = rate constant
    
    • proportional to reaction rate
  • A is the pre-exponential factor
    
    • related to the number of collisions between reactant molecules

Question 4

Rearrange the equation to give ln k ?

Answer 4

• ln k = ln A - (E_a / RT)

Question 5

How can E_a be determined?

Answer 5

• plot graph of ln A over 1 / T
• gradient = -(E_a / R)
  
  • x by R to find activation energy
• ln k = ln A - Ea / RT
  
  • = ln A - Ea / T x 1 / T

Question 6

WHen is the rule - with each 10 K rise in temperature the rate of reaction doubles - applicable?

Answer 6

• around room temp
• activation energy around 50 kJ mol^-1