the iodide ion concentration in the mixture is=iodide concentration in dissociation of barium iodide plus iodide concentration in dissociation of sodium iodide
The ionic equation for dissociation of barium iodide is
BaI2 ---> Ba2+ + 2 I-
Since the ratio of Bal2 to l- is 1:2 hence concentration of iodide ions is 2 x0.193 =0.386M
the ionic equation for dissociation of sodium iodide
Nal--->Na+ + l-
since the ratio of Nal to l- is 1:1 the concentration of iodide ion is o.250M
The concentration of iodide in the mixture is therefore 0.386M +0.250M=0.636M
