1. Calculate the theoretical lattice energy of MgO using both theoretical equations and using a Born-Haber cycle. How do the three values compare? MgO crystallizes in the rock salt structure, the same as NaCl. Are the values you found reasonable compared to the lattice energy of NaCl (787.1 kJ/mole) determined in class? Explain why or why not. The necessary data is found below.
2. Al is a metal while the adjacent element, Si, is a semiconductor. Explain, in terms of band theory, why this change occurs.
3. Predict the products and balance the following reactions:
a. H2SO4(aq) + Na2O(s)
b. F3B-S(CH3)2(solvate) + CH3NH2(g)
c. [CuI4]2–(aq) + [CuCl4]3–(aq)
4. Calculate ΔH° for the reaction in question 3b. Hint: Use a thermochemical cycle.
5. Balance the reaction for the disproportionation of AgO. Find the standard potential for this reaction. Is the reaction spontaneous or not?
Potentially Useful Information:
Born-Landé: Elat = –NAAZ+Z–e2(1 – 1/n)/4πεodo
Born-Mayer: Elat = –NAAZ+Z–e2(1 – d*/do)/ 4πεodo
e = 1.602×10–19 C 4πεo = 1.113×10–10 J–1C2m–1 A (rock salt) = 1.748 NA = 6.022×1023
n = 2 (for [He]), = 7 (for [Ne]), = 9 (for [Ar]) d* = 34.5 pm
ElementIE1IE2 EA1EA2r+ (+2) r– (–2)
(kJ/mole)(kJ/mole) (kJ/mole)(kJ/mole)(pm) (pm)
Mg7371476 0NA72 300
O13143386 141–78050 140
ΔHf° (MgO) = –601.6 kJ/mole S(Mg) = 146 kJ/mole Bond Energy O2 = 497 kJ/mole
Drago-Wayland: –ΔH° = EAEB + CACB
CompoundEC
BF320.23.3
(CH3)2S0.7015.26
CH3NH2EC