To determine the molal concentration we:
[tex]\begin{gathered} molality=\frac{moles\text{ }solute}{kg\text{ }solvent} \\ \\ moles=\frac{mass}{molar\text{ }mass} \\ \\ _nKBr=\frac{4.21g}{119gmol^{-1}} \\ _nKBr=0.0354mol \\ \\ molality=\frac{0.0354mol}{0.797kg} \\ molality=0.044m \end{gathered}[/tex]Answer: 0.044 molal
