DESCRIPTIVE INORGANIC CHEMISTRY April 19, 2012 INSTRUCTIONS: PRINT YOUR NAME > NAME.

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1 DESCRIPTIVE INORGANIC CHEMISTRY QUIZ IV April 19, 2012 INSTRUCTIONS: PRINT YOUR NAME > NAME. SHOW YOUR WORK FOR PARTIAL CREDIT THE LAST PAGES ARE a Table of Bond energies and A Periodic Table Work 1-3 of these (45 pts) R = lit-atm/mol-k 1 (15) R = J/mol-K 2 (15) h = X J-s 3 (15) Work 5 of these (50 pts. you may omit 2) c = X 10 8 m/s 4 (10) J = (kg-m 2 )/s 2 5 (10) 6 (10) 7 (10) 8 (10) 9 (10) 10 (10) Free points _5 (5) l TOTAL(100)

2 1. Given the following data, construct the Born-Haber cycle to estimate the Enthalpy of formation for Na 2 O. (Remember this is for formation of one mole of the substance) (Caution: I have included some irrelevant data in the table.) Enthalpy Values kj/mol Na atomization +498 O=O bond energy st electron affinity of Na st ionization of Na nd ionization of Na st Electron affinity of O nd Electron affinity of O st Ionization energy of O nd Ionization energy of O Estimated lattice energy Na 2 O -2486

3 2.(a) For the reaction shown in (b), assign oxidation numbers to Cr and Cl in each compound. Identify which species is oxidized and which is reduced. CrO 2-4 (aq) Cr 3+ (aq) ClO (s) ClO 2 (aq) Cr oxidation number Cr oxidation number Cl oxidation number Cl oxidation number Species reduced Sspecies oxidized (b) Balance the following redox equation in acidic solution by the method of half reactions. Show your work. CrO 4 2- (aq) + ClO (s) Cr 3+ (aq) + ClO 2 (aq)

4 3. For each of the following pairs acids of (a)-(c), identify the stronger Brønsted-Lowry acid in each pair and give a reason for your choice. For each of the pairs of bases (e )-(g), identify the stronger Brønsted-Lowry base in each pair and give a reason for your choice. Acids (a) H-ClO H ClO 2 (b) Li + (aq) K + (aq) (c) Ti 4+ (aq) K + ( aq) Bases (d) Cl - (aq) S 2- (aq) (e) PO 4 3- NO 2 - (f) SO 4 2- SO 3 2- (g) CO 3 2- NO 3 -

5 4. (a) Using Bond Energy table at the end of the quiz, estimate the enthalpy of the following reaction. 5. Given that the enthalpy of atomization of one mole of P is +317 kj/mol, and the bond energies listed in the table at the end of the quiz, estimate the enthalpy of formation of PF 3 (one mole) using a diagram like a Born-Haber cycle. The actually value is -919 kj/mol. Explain why your value is not exactly equal to the true value.

6 6. (a)write the equation for the weak acid HCN reacting as a Brønsted-Lowry acid towards water. (b) Write the equation for the weak base OCl - reacting as a Brønsted-Lowry base towards water. 7. (a) Write an equation for the autoionization of the polar aprotic solvent BF 3. (b) NaF reacts as a base in BF 3. Write an equation for NaF behaving as a base reacting with solvenf BF 3. (c) SnF 2 acts as an acid in BF 3.. Write an equation for SnF 2 behaving as a acid reacting with solvenf BF 3. Hint the Tin product has a (2-) charge. 8. (a) Is the following reaction likely to occur in the gas phase? Give your reasons why. CoF 2 (g) + HgBr 2 (g) HgF 2 (g) + CoBr 2 (g) (b) In the following aqueous solution equilibria, will the products or the reactants be favored? AgF (aq) + LiI(s) AgI (s) + LiF(aq)

7 9. Calcium chloride, CaCl 2, is about four times more soluble than barium chloride, BaCl 2. (a) Explain this trend in terms of hard soft acid base theory. (b) Explain this trend in terms of the thermodynamics of the solution process. 10. Explain how an unstable product can be isolated from a reaction such as was described in the text for the burning of NH 3. The normal product of this combustion is the unreactive compound dinitrogen, N 2. How could one isolate an unfavored, but industrially useful product such as nitrogen monoxide, NO?

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