Chem202_EXAM3ans - Chem 202-01 1. EXAM III - ANSWER KEY...

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Chem 202-01 EXAM III - ANSWER KEY Apr. 9, 2007 1. (30 pts) Indicate whether each statement is True (T) or False (F). Make certain T or F is clearly indicated. Warning: an automatic 0 will result if all the statements are marked the same (all T or all F)! T In the reaction of BCl 3 and NH 3 , BCl 3 is a Lewis acid. T The pOH value decreases with increasing [OH ]. F A 0.1M weak acid with p K a = 4.56 will be an effective buffer at pH = 6.5. T The shape of the complex Fe(H 2 0) 6 3+ is octahedral. T Sulfite is a base. F When a weak acid is titrated with a strong base, pH = p K a at the equivalence point. T The standard molar enthalpy of N 2 ( g ) is zero. F The standard molar entropy of N 2 ( ) is zero. F Any reaction occurs spontaneously and quickly when Δ G < 0 . F The entropy of the universe decreases toward a minimum. 2. (10 pts) Calcium propanoate [Ca(CH 3 CH 2 COO) 2 ] is a mold inhibitor. Circle the pH of a solution made by dissolving 6.05 g of Ca(CH 3 CH 2 COO) 2 in water to give 0.500 L of solution. E. 9.00 Pr + H 2 O HPr + OH M Ca Pr 2 = 40.08 + 6 12.01 + 10 1.008 + 4 16.00 = 186.22 n Ca Pr 2 = 6.05g mol 186.22g = 0.0325mol and Pr = 2 n Ca Pr 2 V = 2 0.0325mol 0.500L = 0.130M K b = HPr [ ] OH Pr = 1.0
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Chem202_EXAM3ans - Chem 202-01 1. EXAM III - ANSWER KEY...

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