- #1

Frigus

- 337

- 157

Can you please tell me how he relates probability to molarity.

Thanks

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter Frigus
- Start date

- #1

Frigus

- 337

- 157

Can you please tell me how he relates probability to molarity.

Thanks

- #2

Borek

Mentor

- 29,172

- 3,848

Broadly speaking he never claims the probability to equal molarity, he says they are related by which he means they are directly proportional - there is some scaling factor that converts the concentration into probability. Imagine you have a mixture of 1 M N

However, his "explanation" is convoluted to the point of being completely useless, plus the idea of "probability that things are going to react just because they happen to be in the same place" doesn't make sense to me.

- #3

TeethWhitener

Science Advisor

Gold Member

- 2,445

- 1,997

This refers to the pre-exponential factor in the Arrhenius equation. Just because two molecules collide, doesn't mean they'll react. They have to have sufficient energy, be in the correct orientation, be in the correct quantum vibrational and electronic states, etc. So given a collision between two molecules, there is a certain probability that they'll react with each other based on those considerations.the idea of "probability that things are going to react just because they happen to be in the same place" doesn't make sense to me.

- #4

Frigus

- 337

- 157

Thanks sir,Broadly speaking he never claims the probability to equal molarity, he says they are related by which he means they are directly proportional - there is some scaling factor that converts the concentration into probability. Imagine you have a mixture of 1 M N2 and 2 M H2 - if you draw a random molecule from the mixture probability that it is nitrogen or hydrogen definitely depends on their concentrations, but is never equal to them.

Now my misconception about it is cleared.

- #5

Borek

Mentor

- 29,172

- 3,848

This refers to the pre-exponential factor in the Arrhenius equation. Just because two molecules collide, doesn't mean they'll react. They have to have sufficient energy, be in the correct orientation, be in the correct quantum vibrational and electronic states, etc. So given a collision between two molecules, there is a certain probability that they'll react with each other based on those considerations.

Yes, but he calculates "probablity" using just the presence of molecules in dV and not saying anything about the fact some of the collisions are inactive. For me that's - from pedagogical point of view - just replacing one nonintuitive information with another, I don't see how it can help in understanding the idea of equilibrium.

In other words: IMHO he doesn't explain anything, just does some convoluted hand waving for 15 minutes.

- #6

TeethWhitener

Science Advisor

Gold Member

- 2,445

- 1,997

- #7

Frigus

- 337

- 157

- #8

Borek

Mentor

- 29,172

- 3,848

The probability of them reacting is directly proportional to the rate.

- #9

Frigus

- 337

- 157

Thanks,The probability of them reacting is directly proportional to the rate.

So we can get rate by multiplying probability with some constant.

- #10

Borek

Mentor

- 29,172

- 3,848

Yes.

Share:

- Replies
- 23

- Views
- 1K

- Last Post

- Replies
- 6

- Views
- 944

- Replies
- 8

- Views
- 703

- Replies
- 3

- Views
- 1K

- Replies
- 1

- Views
- 1K

- Replies
- 3

- Views
- 78

- Last Post

- Replies
- 3

- Views
- 593

- Replies
- 3

- Views
- 374

- Last Post

- Replies
- 11

- Views
- 158

- Replies
- 3

- Views
- 1K