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This document includes instructions and problems for Chem 101, Week #6 discussions.
Students are instructed to show all work and include units in their answers when appropriate.

Predict Greater Lattice Energy (more negative) for the following pairs:
- NaCl or LiF:
  - LiF is expected to have a greater lattice energy than NaCl due to the higher charge density of Li+ compared to Na+, as well as the smaller ionic radius of F- relative to Cl-.
- MgCl2 or MgO:
  - MgO will have a greater lattice energy because of the larger charge on the ions (Mg2+ and O2-) compared to MgCl2 (Mg2+ and Cl-). The increased charge leads to a stronger electrostatic attraction.
- CaCl2 or CaBr2:
  - CaCl2 will have greater lattice energy than CaBr2 due to Cl- having a smaller ionic radius than Br-, resulting in stronger ionic interactions.

To solve for the lattice energy change (∆H◦latt) for Na2O, consider the following energy values that need to be looked up:
- Ionization energies of sodium (two values for Na since it's Na2O).
- Electron affinity of oxygen.
- Enthalpy of formation of Na2O.
- Bond dissociation energies related to the formation process.

Draw Dipole Arrows to Show Charge Separation: For each bond listed below:
- a. O - F: Dipole arrow should point towards F (F is more electronegative).
- b. O - Cl: Dipole arrow points towards Cl.
- c. O - Br: Dipole arrow points towards Br.
- d. O - I: Dipole arrow points towards I.
- Circle the Bond with Greatest Charge Separation:
  - O - F is expected to have the greatest charge separation due to fluorine being the most electronegative element in the periodic table, leading to a strong dipole moment.

Oxygen Difluoride (OF2): Draw the best Lewis Structure for OF2, ensuring that all atoms have complete octets where possible and follow the octet rule.
Sulfate (SO2−4) Lewis Structures:
- Draw two Lewis structures for sulfate:
  - One Structure following Octet Rule: Ensure each atom has eight electrons.
  - One Structure Minimizing Formal Charge: Consider charging involving Lewis structures to have the least amount of total formal charges.

NH3 and PH3 Bond Angles:
- Bond Angles: NH3 = 107°, PH3 = 93°.
- Electron Pair Geometry: Both have tetrahedral electron pair geometry due to lone pairs and three bonded atoms.
- Molecular Geometry: Both are trigonal pyramidal.
- Explanation of Different Bond Angles: The differences are due to the larger size of phosphorus compared to nitrogen leading to lesser lone pair-bond pair repulsion in PH3 than in NH3. This results in a smaller bond angle in PH3 due to the greater size and lower electronegativity of P compared to N.

Lewis Structure for Dinitrogen Monoxide (N2O):
- Draw the Lewis Structure and any possible resonance structures.
- Consider which resonance structure is the most representative of the overall structure, usually the one minimizing formal charges.

Comparison of Lewis Structures of Isomers (Same molecular formula, different connectivity):
- Draw Lewis Structures for:
  - Nitrosyl cyanide (ONCN): Minimize formal charge.
  - Isonitrosyl cyanide (NOCN): Minimize formal charge.
  - Nitrosyl isocyanide (ONNC): Minimize formal charge.
- Given Bond Dissociation Energies (in kJ/mol):
  - C-O: 336
  - N-N: 160
  - C-N: 285
  - N-O: 201
  - C=O: 695
  - N=N: 418
  - C=N: 616
  - N=O: 629
  - C≡O: 1073
  - N≡N: 941
  - C≡N: 866
- Calculate the reaction enthalpy (∆Ho rxn) for converting isonitrosyl cyanide to nitrosyl cyanide using the provided bond dissociation energy data. Assess from the bond energies, which molecule has stronger bonds based on the energies involved.