# Worksheet: Molecular Bonds

Q1:

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 .

Q2:

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.

Q3:

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 μ for the HCl molecule.

• A0.69 u
• B0.32 u
• C0.54 u
• D0.97 u
• E0.27 u

Find the separation distance between the H and Cl atoms.

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/cm3. Coulomb’s constant is N⋅m2/C2.

Q5:

What value of the repulsion constant, , gives the measured dissociation energy of 171 kcal/mol for KCl? The molar mass of KCl is 74.55 g/mol and its density is 1.98 g/cm3. Coulomb’s constant is N⋅m2/C2.

Q6:

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.

Q7:

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.)

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:

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⋅m2/C2. Give your answer in electron-volts (eV).