In this worksheet, we will practice calculating the dissociation energies of different ionic, covalent, and van der Waals molecular bonds.

**Q1: **

Potassium chloride (KCl) is a molecule formed by an ionic bond.
At equilibrium separation, the atoms are nm
apart. Determine the electrostatic potential energy of the atoms given that coulomb’s constant is
N⋅m^{2}/C^{2}.
Give your answer in electron-volts (eV).

**Q2: **

Potassium fluoride () is a molecule formed by an ionic bond. At equilibrium separation the atoms are apart. Determine the electrostatic potential energy of the atoms. The electron affinity of is 3.40 eV and the ionization energy of is 4.34 eV. Determine dissociation energy. (Neglect the energy of repulsion.)

**Q3: **

What value of the repulsion constant, , gives the measured
dissociation energy of 171 kcal/mol
for
? The molar mass of is 74.55 g/mol
and its density is 1.98 g/cm^{3}.
Coulomb’s constant is N⋅m^{2}/C^{2}.

**Q4: **

Determine the dissociation energy of 12.0 moles of sodium chloride (NaCl). Use a repulsion constant for NaCl of 8.00 and a Madelung constant of 1.75. The molar mass of NaCl is 58.44 g/mol and its density is 2.16 g/cm^{3}. Coulomb’s constant is N⋅m^{2}/C^{2}.

**Q5: **

The measured density of a crystal is 4.51 g/cm^{3}.
Find the equilibrium separation distance of and
ions. Use a value of 259 g/mol for the molar mass of .

**Q6: **

The electron affinity of Br is 2.18 eV and the ionization energy of Na is 5.14 eV. NaBr forms an ionic bond. At equilibrium separation, the atoms are apart.

Determine the electrostatic potential energy of the atoms.

Find the dissociation energy. Neglect the energy of repulsion.

**Q7: **

What value of the repulsion constant, , gives the measured dissociation energy of 188 kcal/mol for NaCl? Use a value of 1.75 for the Madelung constant and a value of 0.281 nm for the equilibrium separation of Na and Cl. Give your answer to two significant figures.

**Q8: **

The measured density of a crystal is 2.75 g/cm^{3}. Find the equilibrium separation distance of and ions. Use a value of 119.003 g/mol for the molar mass of .