October 17, 2019, 02:15:56 PM
Forum Rules: Read This Before Posting Topic: ion activity  (Read 5012 times)

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jay

• Guest ion activity
« on: August 22, 2004, 03:44:42 AM »
Hey, im having trouble with the below problem, i know which formulas must be used and understand how to calculate the ionic strength, which is equal to 0.25, but am stuck calculating the activity coefficient.

Problem : The permanganate ion activity in a
0.05M KMnO4 solution is
a)0.616
b)0.066
c)0.023
d)0.31
e)0.040

Any help would be great
thanks

Demotivator

• Guest Re:ion activity
« Reply #1 on: August 23, 2004, 10:44:34 AM »
It would be nice if you provide the equation you're using to calculate activity coefficient. If it's the extended equation:

-Log(f) = [(0.51 x Z2 x SQRoot(I)) / (1 + (3.29 x d x SQRoot(I))] - (0.1 x Z2 x I)
Where: Z = the ionic charge, I = the ionic strength of the solution, d = the ionic radius in nanometres.
Then for a value of d = .35 (an educated guess for mno4-):
I get f = 0.73
activity = .73(.05M) = .036