Chapter 10, Problem 112AE

Consider the following enthalpy changes:

$\begin{array}{c}{\text{F}}^{-}+\text{HF}\to {\text{FHF}}^{-}\text{ΔH}=-155\text{kJ}/\text{mol}\\ {\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{C}=\text{O+HF +}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{C}═\text{O---HF}\Delta H=-46\text{kJ}/\text{mol}\\ {\text{H}}_{\text{2}}\text{O}\left(\text{g}\right)+\text{HOH}\left(\text{g}\right)\text{+}{\text{H}}_{\text{2}}\text{O---HOH}\left(\text{in}\text{ice}\right)\Delta H=-21\text{kJ}/\text{mol}\end{array}$

How do the strengths of hydrogen bonds vary with the electronegativity of the element to which hydrogen is bonded? Where in the preceding series would you expect hydrogen bonds of the following type to fall?