[AWK]

And now correct this value with ionic strenght of solution.

[BHAVESH]

can you please give some hint??

[AWK]

Calculate activity coefficients.

[BHAVESH]

Shall I use Davies Equation?

Log[γ_z ]= -A* Z² [√I/(1+ √I)]-0.3I
A = 1.82X106*[ET]^-1.5
E = 60954/[T + 116] - 68.937

T = Temp in °K
I = Ionic Strength

[AWK]

For the beginning use standard temperature 25°C.
Check your Davies equation for the correct syntax.

[BHAVESH]

Thanks AWK

Log[γ_z]= -A*Z²[√I/(1+ √I)-0.3I]

I hope this is correct now. Thanks

[BHAVESH]

I Calculated Activity Coefficients
Ionic Strength - 0.2499
Temp. - 25°C = 298.15°K
A Value - 0.511
E Value - 78.24

Ionic Charge            γ Value   
      1                      0.738   
      2                     0.297   
      3                     0.065   
      4                     0.008   

Now, what should be the next step?

[AWK]

For the problem given by Borek, the ionic strength is close to 0.04.

[BHAVESH]

Ok
Ionic Strength is 0.04 using I = 0.5ΣC_iZ_i²
Temp. - 25°C = 298.15°K
A Value - 0.511
E Value - 78.24
For,
Ionic Charge     γ Value
       1                 0.834
       2                 0.483

[AWK]

Now calculate pH of this solution with activity coefficients and compare with the value obtained without activities.

[BHAVESH]

Ok
Ionic Strength is 0.04 using I = 0.5ΣCiZi2
Temp. - 25°C = 298.15°K
A Value - 0.511
E Value - 78.24
For,
Ionic Charge     γ Value
       1                 0.834
       2                 0.483
Division of γ Value = 0.834/0.483 = 1.7267
K - 4.8 X 10^-11
K' =4.8 X 10^-11 X 1.7267 = 8.2882 X 10^-11
Corrected pH = -Log[K'] = 10.082
Original pH is 10.32

Please correct me if I am wrong.

[AWK]

And where is the activity of H⁺ ions?

[BHAVESH]

Ok
Ionic Strength is 0.04 using I = 0.5ΣCiZi²
Temp. - 25°C = 298.15°K
A Value - 0.511
E Value - 78.24
For,
Ionic Charge     γ Value
       1                 0.834
       2                 0.483
Division of γ Value = (0.834 X 0.483)/0.483 = 0.834 (Product/Reactant)
K - 4.8 X 10^-11
K' =4.8 X 10^-11 X 0.834 = 4.0032 X 10^-11
Corrected pH = -Log[K'] = 10.40
Original pH is 10.32

Does it mean that pH always increases when we use Ionic Strength as a correction factor, OR does it depend upon what kind of Acid, Base or salt reaction we work with???

Please correct me if I am wrong.

[AWK]

The value of K' is ambiguous. What exactly does it mean for you? Calculations can be made using the thermodynamic constant K. I expect a pH value very close to 10.

[BHAVESH]

What I think is that at constant temperature, ionic strength affect K value OR pH Value. When It is corrected using ionic strength, gives us actual value.

Can you please give me some hint on using thermodynamic constant K?