Question

$10$ g of NaCl is dissolved in $250$ g water. The correct way to express concentration of NaCl in solution are :

• A. mass fraction = 0.04
• B. mole fraction = 0.0122
• C. molality =0.684
• D. molarity =0.684

Answer 1

Answer: (B), (C)

molality =0.684
mole fraction = 0.0122

Mass fraction $=\frac{10}{260}$
Mole fraction $=\frac{\left(10/58.5\right)}{\left(\right(10/58.5)+(250/18\left)\right)}=0.0122$
Molality $=\frac{10}{58.5}\times \frac{1000}{250}=0.684$