Hard Practice — Advanced Set

Quick Recap — Molar Mass & Van't Hoff Calculations (Hard)

• Molar mass from colligative data: $M=\dfrac{K_f\,w_2\,1000}{\Delta T_f\,w_1}$ (or the analogous $K_b$/$\pi$ form).
• $\Delta T_f=iK_f m$, $\Delta T_b=iK_b m$, $\pi=iMRT$; $i=1+\alpha(n-1)$ (dissociation) or $i=1-\alpha(1-\tfrac1n)$ (association).
• Convert between molality and mole fraction via solvent mass; isotonic $\Rightarrow$ equal $iM$.
• Use $K_f=1.86$, $K_b=0.52$ (water), $R=0.0821$ L$\cdot$atm/mol$\cdot$K.