2010 Chemistry 2353 Assignment 4 1. (6 points) Consider three possible ionic compounds formed by barium and oxygen, Ba + O-, Ba 2+ O 2-, Ba 3+ O 3-. a) which would have the greatest lattice energy? b) which would require the least energy to form ions? c) which compound actual exists and why? 2. (3 points) The process O(g) + 2e O 2-(g) absorbs 653 kJ/mol. In view of this, explain why so many ionic oxides exist? 3 . (4 points) The molecular masses of CH 3 NH 2 and CH 3 F are approximately equal, but the boiling points are -6.5 o C and -78.4 o C, respectively. Explain this difference. 4. A zinc-copper battery is constructed from metallic zinc and copper electrodes, and 1 L of electrolyte containing 0.1 M Zn 2+ and 2.5 M Cu 2+ . The mass of each electrode is 200 g. Cu + (aq) + e Cu(s) E o =0.521 Cu 2+ (aq) + e Cu + (aq) E
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