# Worksheet: Molecular Bonds

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

Q1:

Potassium chloride is a molecule formed by an ionic bond. At equilibrium separation, the atoms are apart. Determine the electrostatic potential energy of the atoms given that coulomb’s constant is N⋅m2/C2. 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 701 kJ/mol for ? The molar mass of is 74.55 g/mol and its density is 1.98 g/cm3. Coulomb’s constant is N⋅m2/C2 and Madelung constant 1.7476.

Q4:

Determine the dissociation energy of 12.0 moles of sodium chloride (). Use a repulsion constant for of 8.00 and a Madelung constant of 1.75. The molar mass of is 58.44 g/mol and its density is 2.16 g/cm3. Coulomb’s constant is N⋅m2/C2. Take ions and the electronic charge .

Q5:

The measured density of a crystal is 4.51 g/cm3. 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 ? Use a value of 1.75 for the Madelung constant and a value of 0.281 nm for the equilibrium separation of and . Give your answer to two significant figures.

Q8:

The measured density of a crystal is 2.75 g/cm3. Find the equilibrium separation distance of and ions. Use a value of 119.003 g/mol for the molar mass of .

Q9:

The characteristic energy of rotation for HCl is eV, assuming a value of 35.4 u for the atomic mass of chlorine and 1.0 u for the atomic mass of hydrogen.

Determine the reduced mass for the HCl molecule.

Find the separation distance between the H and Cl atoms.