CHEM 1A: Challenge Problem Set 6
1. Choose the LOWEST ENERGY Lewis dot structure for the neutral molecule: N2O.
Hint: Be sure to minimize formal charge.
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2. An unknown mineral composed of iron and sulfur was discovered in San Bernardino County. An analysis of a
21.128 g sample was found to contain 9.161 g of sulfur. Using information on the mass composition of the
mineral, determine the empirical for the unknown substance.
3. Al(s) + 3/2 F2(g) → AlF3(s)
ΔE = ? kJ/mol
With the reference information provided below, use a Born-Haber cycle to calculate the energy absorbed (+) or
released (-) for the reaction above.
TIP: Not all of the reference information below may be necessary for the solution. The final answer should be
reported in kJ/mol. Be sure to include the phase to specify if energy is released or absorbed.
Reference Information:

1st Ionization Energy of Aluminum: +578 kJ/mol
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2nd Ionization Energy of Aluminum: +1817 kJ/mol
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3rd Ionization Energy of Aluminum: +2745 kJ/mol
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4th Ionization Energy of Aluminum: +11575 kJ/mol
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5th Ionization Energy of Aluminum: +14830. kJ/mol
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Sublimation Energy of Aluminum: +330 kJ/mol

1st Electron Affinity of Fluorine: -328 kJ/mol

Bond Energy for F--F bond: +159 kJ/mol

Lattice Energy for AlF3(s): +5215 kJ/mol