[faizan]

If a reaction takes place in more than one step, then the rate determining step is the slowest step? Why is it so?

[fledarmus]

What determines how long you spend trying to get a license at the Department of Motor Vehicles? Filling out the form? Having the person behind the desk look at your paperwork? Getting your picture taken? Or standing in line behind 300 people all trying to get the same thing done?

When you tell your boss, "I'm taking ___hours off to go get my driver's license renewed", what is determining how many hours you need?

How about applying for a passport? Why does it take six weeks to arrive? What would be the rate determining step of that process? Downloading the form from the computer? Filling it out? Taking it in to the post office? Opening the envelope when it arrives back at your house? Or the five and one-half weeks it sits in the State Department, waiting to reach the top of somebody's inbox?

[juanrga]

If a reaction takes place in more than one step, then the rate determining step is the slowest step? Why is it so?

What is more close 100+1? 100 or 1?

[faizan]

How about applying for a passport? Why does it take six weeks to arrive? What would be the rate determining step of that process? Downloading the form from the computer? Filling it out? Taking it in to the post office? Opening the envelope when it arrives back at your house? Or the five and one-half weeks it sits in the State Department, waiting to reach the top of somebody's inbox?

the five and one-half weeks it sits in the State Department, waiting to reach the top of somebody's inbox?

[faizan]

What is more close 100+1? 100 or 1?
[/quote]
100

[fledarmus]

Exactly. Most of the other things going on the reaction, like salts dissociating or bonds rotating, are happening fast enough that they are insignificant in terms of determining the rate of the reactions. The slowest step of the reaction is the choke point, and it determines the rate of the entire reaction.

[juanrga]

What is more close 100+1? 100 or 1?
100

Then if you have a two steps reaction the first finishing in 0.1 seconds and the second step finishing in 5 minutes, the overall rate of the reaction will be determined by the slow step and you will wait about 5 minutes before the reaction is complete.

[faizan]

What determines how long you spend trying to get a license at the Department of Motor Vehicles? Filling out the form? Having the person behind the desk look at your paperwork? Getting your picture taken? Or standing in line behind 300 people all trying to get the same thing done?

When you tell your boss, "I'm taking ___hours off to go get my driver's license renewed", what is determining how many hours you need?

standing in line behind 300 people all trying to get the same thing done

[awkko808]

If the multi-step reaction A + B -> C + D is composed by elementary reactions:

1. A + A -> C + E (fast)
2. E + B -> A + D (slow)

Then you can compare reaction #1 as pouring water into a funnel, and reaction #2 as the water leaving the stem. The slowest reaction produces a bottleneck effect and therefore limits the overall rate of the multi-step reaction.