which of the following aqueous solutions of Na2SO4 is isotonic?

Question

with 0.15 M NaCl solution? 0.05M,0.10M, or 0.15M,,or none of them

Answer 1

For electrolytes
π = iCRT

where i is the Van't Hoff coefficient and (for simplicity) it is equal to the number of ions that a strong electrolyte dissociates into according to its molecular formula.

For NaCl i=2, so
π =2*0.15RT= 0.3RT

For Na2SO4 i=3, so
π =3*0.05RT= 0.15RT
π =3*0.10RT= 0.3RT
π =3*0.15RT= 0.45RT

So 0.10 M Na2SO4 is isotonic to 0.15 M NaCl