Potassium chloride, bond energy

Now it is known that this is not true for all substances the examples of cadmium, sodium chloride, and potassium chloride were cited in Section III. A, where the lack of wetting behavior led to an experimental method for measuring ffj,. If, however, this result is assumed to hold true, then the calculation reduces to a calculation of and a separate calculation or measurement of ff( . Skapski then estimates the difference in energy of the bonds broken to form the solid-vapor and liquid-vapor interfaces from the enthalpy of fusion of the bulk solid and the volume change on melting, and adds to it a small estimated contribution from the entropy change in the outer layer of the liquid and of the solid. The result is... 

The lattice energy of sodium chloride, NaCl, is —787.5 kj/mol. The lattice energy of potassium chloride, KCl, is —715 kf/mol. In which compound is the bonding between ions stronger Why ... 

Energy is needed to break the ionic bonds in the solid salt and energy is liberated forming hydration complexes like VI. We also break some of the natural hydrogen bonds in the water. The overall change in enthalpy is termed the enthalpy of solution, A// olutioni. Typical values are —207 kJmol-1 for nitric acid 34 kJmol-1 for potassium nitrate and —65.5 kJmol-1 for silver chloride. 

The effects of DN on the solvation energy of the potassium ion and on the standard potential of the hydrogen electrode, which is linearly related to the solvation energy of the hydrogen ion, are shown in Fig. 2.3. Near-linear relations can be observed in both cases [13]. There is also a linear relationship between AN and the solvation energies of the chloride ion in aprotic solvents, as in Fig. 2.4 [13]. However, the chloride ion in protic solvents like water and alcohols behaves somewhat differently than in aprotic solvents [14], probably because of the influence of hydrogen bonding (see below). 

We note that Cotton and Jenkins (4) in the same paper reported bond dissociation energies for LiOH(g) and KOH(g) which are in reasonable agreement with JANAF values (5) for the enthalpy of formation of these two compounds. Furthermore, bond dissociation data for the alkali metal halides ( ) clearly establish the sodium compound as the least stable within each halide series. The potassium and sodium compounds differ by from 4.3 kcal mol for the fluorides and bromides to 3.6 kcal mol for the chlorides. 

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