Question

Find the molality of a 8 M NaOH solution having a density of 1 g/mL.

• A. $10.20m$
• B. $11.76m$
• C. $13.75m$
• D. $12.25m$

Answer 1

The correct option is B $11.76m$

Let, the mass of the solution be 1000 mL.
Therefore, 8 M NaOH solution means 8 moles of NaOH is present in 1000 mL solution.

Given:
Density of the solution = 1 g/mL
Therefore, mass of the solution $=1\times 1000g$
Mass of NaOH $=8\times 40g=320g$
Therefore, mass of the solvent
$=(1000-320)g=680g=0.68kg$

Hence,
$\text{molality}=\frac{8}{0.68}=11.76m$