## roselin Group Title what does the following mean? Calculate single ion activity coefficients for Cs^+, Cd^2+,Al^3+ and dissolved H2CO3 as a function of ionic strength for 10^-4 lessthan equal I lessthan equal to1? 9 months ago 9 months ago

1. aaronq Group Title

they want the activity coefficients for the different ions considering the ionic strength given

2. roselin Group Title

so from 10^-4 to 1?

3. roselin Group Title

i am using the davies equation to calculate it, so each time I have to change the ionic strength th?

4. aaronq Group Title

hm no that doesn't seem right. i don't know what they mean by $$10^{-4} \leq 1$$, it doesn't make sense.

5. roselin Group Title

its $10^{-4}\le I \le1$

6. aaronq Group Title

oh, i thought you typed the same thing twice accidentally. I guess they want it within that range? thats a large range though. I would graph it

7. aaronq Group Title

on excel of course

8. roselin Group Title

we have to calculate and plot it

9. aaronq Group Title

i guess do a few points for each ion and then plot it

10. roselin Group Title

can I show you the full question ? please tell me what I should do

11. aaronq Group Title

plug it into the formula? $$log\;\gamma=0.5Z^+_0Z^-_0.. etc$$ it's kinda weird though because they don't give you the negative counter ion

12. roselin Group Title

if I were to do this manually using that given range, how would I approach it?

13. aaronq Group Title

you would calculate the coefficient for several points (ionic strengths) do 3 or 4, then plot these. Activity coefficient on the y axis and ionic strength on the x axis (although you can do on which every way you want)

14. aaronq Group Title

it's much easier if you do it in excel though

15. roselin Group Title

yes, that is where I am having problem.

16. roselin Group Title

like that range is between 10^-4 to 1 right?

17. aaronq Group Title

yep thats the range of "I" they gave

18. roselin Group Title

how would I calculte that in excel though?

19. roselin Group Title

if I do it manually then can I chose to do something like I= 10^-4,10^-3, 10^-2 and 10^-1?

20. roselin Group Title

choose**

21. aaronq Group Title

yeah thats fine

22. aaronq Group Title

for excel you need the x data point and the y data point the x you can just make up: 10^4, 10^3 then for the y you have to use the result from the equation, so you would type up the equation and use the x data points, then fill it. If you're not familiar with excel trying it this way might take you awhile

23. roselin Group Title

okay, thank you so much.

24. aaronq Group Title

no problem, good luck!

25. roselin Group Title

thanks :-)