Calculate ionic strength and mean ionic activity coefficient?

Question

Is there any easy way to do this or is it just a ridiculously large equation I need to use?

The question is...Calculate the ionic strength for an aqueous solution with 0.002 mol/kg NaCO3

and next question says to estimate the mean ionic activity coefficient of the aqueous solution at 25 degrees C.

I really dont want to do this but I must!
If you answer, please explain, this is just a sample question to prepare me for a test so straight up answers are of no use to me! Ta:)

Answer 1

if ci and zi are the valence and the normality of ions
ionic strength is

IS= sum of 1/2 ci*zi^2

your formula is wrong it is Na2CO3

Na2CO3--> 2Na+ + CO3-
z Na+=1 z CO3=2 cNa+ =0.004 c CO3 =0.002
IS= 1/2*(0.004*1+0.002*4)=0.006

For the next question, i must know the equilibrium constant of dissociation , sorry

Answer 2

Activity Coefficient Calculator

Answer 3

To get the ionic strength you need to sum over all the ions

I = 1/2(sum M * Z^2)

Z = charge on the ions, M is the molality
don't forget sodium carbonate is Na2 CO3 so the conc of Na is 0.004 M.

Use the Debye-Huckel limiting law to get the activity coeff.