Isotonic solutions are those which have the same osmotic pressure (π=iCRT). But here we have different concentration of the solutions and also they have different Van't Hoff factors (i). So the solutions for which the product of i and c will be the same and isotonic.
a. For, 0.001MCaCl2,i=3.
So i×C=3×0.001=0.003
For, 0.001MAl2(SO4)3,i=5.
So i×C=5×0.001=0.005
b. For, 0.01MBaCl2,I=3.
So i×C=3×0.01=0.03
For, 0.001MCaCl2,i=3.
So i×C=3×0.001=0.003
c. For, 0.01MBaCl2,i=3.
So i×C=3×0.01=0.03
For, 0.015MNaCl,i=2.
So i×C=2×0.015=0.03
Thus 0.01MBaCl2 and 0.015MNaCl are isotonic in nature.
d. For, 0.001MAl2(SO4)3,i=5.
So i×C=5×0.001=0.005