At the same temperature, what mass of $NaCl$ (molar mass $58.5 g mo l^{- 1}$ , assume complete dissociation) per litre of solution is isotonic with $0.30 M$ glucose?

Answer: A

Isotonic means equal total particle concentration.

i C_{N a Cl} = 0.30

with

i = 2

, so

C_{N a Cl} = 0.15

M. Mass per litre

= 0.15 \times 58.5 = 8.78

g. Using

0.30

M of

NaCl

would give 17.55 g, which is twice as much.