  Question

# Which of the following solutions are isotonic with respect to 0.5 M NaCl solution having the degree of dissociation = 0.8.153.9 g of sucrose is dissolved in 500 mL of solution0.3 M aq. Na2SO4 solution undergoing 100% ionization1.8% w/w aq.NaOH solution undergoing 100% ionization1.2 M benzoic acid in a solution of benzene where the acid dimerizes to an extent of 50%

Solution

## The correct options are A 153.9 g of sucrose is dissolved in 500 mL of solution B 0.3 M aq. Na2SO4 solution undergoing 100% ionization C 1.8% w/w aq.NaOH solution undergoing 100% ionization D 1.2 M benzoic acid in a solution of benzene where the acid dimerizes to an extent of 50%At particular temperature isotonic solutions are those which have same solute concentration. For NaCl: ic=0.5×[1+(2−1)0.8]=0.9 M For sucrose solution: ic=153.9342×1000500×1=0.9 M For Na2SO4 solution: ic=0.3×3=0.9 M  For NaOH: Molality =1.840×1000100 For very dilute solutions molality is almost equal to the molarity. Thus ic =1.840×10×2=0.9M For benzoic acid: ic=1.2×[1+(0.5−1)0.5]=1.2×34=0.9 M Solutions having same ic value are isotonic.  Suggest corrections   