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# ionic activity, a+-

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1. may i know how to calculate the ionic activity of an ion, a+-, given the ionic strength, I, concentration in molarity and mean activity coefficient?From what i understand, it cannot be found without molality (m)
2. (Original post by lucasleiva)
may i know how to calculate the ionic activity of an ion, a+-, given the ionic strength, I, concentration in molarity and mean activity coefficient?From what i understand, it cannot be found without molality (m)
Take a look here: http://www.aqion.de/site/69
3. (Original post by alow)
Take a look here: http://www.aqion.de/site/69
hmmm i cant find my answer there?
4. is this formula correct?ionic activity, a+-= activity coefficient multiply with molarity (M)
5. (Original post by lucasleiva)
hmmm i cant find my answer there?

(Original post by lucasleiva)
is this formula correct?ionic activity, a+-= activity coefficient multiply with molarity (M)
Are you sure you read what I posted?

There's also this which is the same thing but prettier: https://web.stanford.edu/~cgong/cee3...3Lecture03.pdf

Also what is a+-? Do you mean ?
6. (Original post by alow)
Are you sure you read what I posted?

There's also this which is the same thing but prettier: https://web.stanford.edu/~cgong/cee3...3Lecture03.pdf

Also what is a+-? Do you mean ?
a+- is mean ionic activity?
7. (Original post by lucasleiva)
a+- is mean ionic activity?
Okay... so did you not read the first site I posted? Everything is explained there.
8. (Original post by alow)
Okay... so did you not read the first site I posted? Everything is explained there.
i did, and it is stated
ai = γi ci, so just multiply molarity with activity coefficientt?
9. (Original post by lucasleiva)
i did, and it is stated
ai = γi ci, so just multiply molarity with activity coefficientt?
Well yeah... that's how you calculate activity. It's calculating where you have to consider Ionic strength.

Is this actually a question which has been given to you? What is the precise wording of the entire question as what you've posted does not make much sense as there are a multitude of answers using different models.
10. (Original post by alow)
Well yeah... that's how you calculate activity. It's calculating where you have to consider Ionic strength.

Is this actually a question which has been given to you? What is the precise wording of the entire question as what you've posted does not make much sense as there are a multitude of answers using different models.
the whole question is calculate the ionic strength, mean activity coefficient and the ionic activity of 0.0325M K4Fe(CN)6 at 298K
11. (Original post by lucasleiva)
the whole question is calculate the ionic strength, mean activity coefficient and the ionic activity of 0.0325M K4Fe(CN)6 at 298K
So have you found any of those yet?
12. (Original post by alow)
So have you found any of those yet?
Ionic strength: 0.325
Mean activity coefficient: 0.06907Mean ionic activity: 0.0325 x 0.06907 = 0.00224
Am i right?
13. (Original post by lucasleiva)
Ionic strength: 0.325
Mean activity coefficient: 0.06907Mean ionic activity: 0.0325 x 0.06907 = 0.00224
Am i right?
Your Ionic Strength is right. Which model did you use to find the activity coefficients?
14. (Original post by alow)
Your Ionic Strength is right. Which model did you use to find the activity coefficients?
Debye Huckel limited law?
15. (Original post by lucasleiva)
Debye Huckel limited law?
If you look on this site: http://www.aqion.de/site/101 it shows that Debye-Huckel is only appropriate for I < 10-2.3M.
16. (Original post by alow)
If you look on this site: http://www.aqion.de/site/101 it shows that Debye-Huckel is only appropriate for I < 10-2.3M.
but the question did not provide me the constant values that can be used for the extended debye huckel limiting rule?
17. (Original post by lucasleiva)
but the question did not provide me the constant values that can be used for the extended debye huckel limiting rule?
Extended Debye-Huckel is also not valid. You should really use the Davies model.

18. (Original post by alow)
Extended Debye-Huckel is also not valid. You should really use the Davies model.

the question just provdide 0.0325M solution of K4Fe(CN)6
19. (Original post by lucasleiva)
the question just provdide 0.0325M solution of K4Fe(CN)6
I would assume it is aqueous then.
20. (Original post by alow)
I would assume it is aqueous then.
may i know is my method of calculating the mean ionic activity is right or wrong?i multiply the activity coefficient with the molarity (0.0325M)

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