Answer :
Answer:
5.85 grams of NaCl should be added to 250 grams of water to make a 0.40 m solution.
Explanation:
[tex]molality=\frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{ Mass of solvent (kg)}}[/tex]
Mass of NaCl =x
Molar mass of NaCl = 58.5 g/mol
Molality of the solution = 0.40 m
Mass of the solvent = 250 g = 0.250 kg (1g = 0.001 kg)
[tex]0.40 m=\frac{x}{58.5 g/mol\times 0.250 kg}[/tex]
[tex]x=0.40 m\times 58.5 g/mol\times 0.250 kg=5.85 g[/tex]
5.85 grams of NaCl should be added to 250 grams of water to make a 0.40 m solution.