Reaction Mechanisms

1
Reaction Mechanisms
2
Reaction Mechanisms

• Most reactions occur in a series of elementary
  steps
• These steps together are called the reaction
  mechanism
• Molecules that form in one step and are consumed
  in the next are called reaction intermediates

3
Reaction Mechanism
Step 1 Step 2
(slow) (fast)
2N2O(g) ? 2N2(g) O2(g)
Intermediate
4
Rate-Determining Step

• Each elementary step has its own rate
• The overall rate of a reaction is determined by
  the rate of the slowest step, the
  rate-determining step (RDS)
• Therefore, the rate law for the rate-determining
  will be the rate law for the overall reaction
• The molar coefficients in the RDS will be the
  exponents in the overall rate law

5
(No Transcript)
6
Reaction Mechanism
Step 1 Step 2
(slow) (fast)
2N2O(g) ? 2N2(g) O2(g)
Intermediate
Overall rate law depends on the RDS. Molar
coefficients of RDS will be the exponents. r
kN2O
7
Practice

• P. 390 2
• P. 391 1,2,3abcd
• Worksheets