Question

use the extended debye-huckel equation to estimate each of the following activity coefficients. assume in each case that the given chemical completely dissolves to form the listed ions. Activity coefficient for Ba^2+ and Cl- in a 0.010 M BaCl2 solution.

Answer 1

To apply debye Huckel equation we need to determine the ionic strength of solution

= 1/2 [Sigma ( C_i Z_i² )]

... = 1/2 ( 0.01 x 2 x 1²  + 0.01 x 2² )

... = 0.03

Substitute the values in extended debye Huckel equation , ie.-

-log f_i   = [0.51Z² ()^1/2 ] / {1 + ()^1/2  }

So, -log f_i ( Ba²⁺ ) = [ 0.51 x 2²  (0.03 )^1/2 ] / { 1 + ( 0.03 )^1/2 }

............................ = 0.3012

& , f_i (Ba²⁺ ) = antilog of ( - 0.3012 )

..........= 0. 4998

...or , = 0.50

Simlarly f_i (SO₄^2- ) is calculated as = 0.50

[ note that charges on Ba²⁺ & SO₄^2- are equal ]