Chem 162-2011 recitation quiz II + solutions

Chem 162-2011 recitation quiz II + solutions - Chem 162...

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Unformatted text preview: Chem 162 Spring 2011 Quiz 1 Version A1 (20 pts./20 min) Name: _______________________ Section 1. When solid NH 4 NO 3 (s) is placed in an evacuated container, the following equilibrium is established. NH 4 NO 3 (s) N 2 O(g) + 2H 2 O(g) The value of K P is 5.86 at 650 o C. Calculate the pressure of N 2 O and H 2 O at equilibrium. NH 4 NO 3 (s) N 2 O(g) + 2H 2 O(g) I Y C-X +X +X E Y - X +X +2X ([N 2 O][H 2 O] 2 ) = 5.86 X x (2X) 2 = 5.86 4X 3 = 5.86 X = 1.14 atm = [N 2 O] 2X = 2.27 atm = [H 2 O] 2. (5 pts.) What is the Bronsted-Lowery definition of an acid? An acid is a proton donor. 3. Discuss the relative acid strengths of HF and HI, and the reasons. HI is a strong acid; HF is a relatively weak acid. There are two competing factors, the electronegativity-induced electron withdrawing effect and the electronegativity-induced electrostatic interaction. HF: F electronegativity-induced electron withdrawing effect weakens the bond, while strong (due to the small distance between +H and the small -F) electronegativity-induced charge-charge interaction strengthens the bond, with the bond strengthening being more dominant than the bond weakening. HI: Smaller I electronegativity-induced electron withdrawing effect sufficiently weakens the bond, while electronegativity-induced very weak charge-charge interaction (due to the large distance between +H and the large -I) strengthens the bond only slightly, with the bond weakening being more dominant than the bond strengthening. Chem 162 Spring 2011 Quiz 1 Version A2 (20 pts./20 min) Name: _______________________ Section 1. When solid NH 4 NO 3 (s) is placed in an evacuated container, the following equilibrium is established. NH 4 NO 3 (s) N 2 O(g) + 2H 2 O(g) The value of K P is 4.86 at 750 o C. Calculate the pressure of N 2 O and H 2 O at equilibrium. NH 4 NO 3 (s) N 2 O(g) + 2H 2 O(g) I Y C-X +X +X E Y - X +X +2X ([N 2 O][H 2 O] 2 ) = 4.86 X x (2X) 2 = 4.86 4X 3 = 4.86 X = 1.07 atm = [N 2 O] 2X = 2.13 atm = [H 2 O] 2. (5 pts.) What is the Bronsted-Lowery definition of an base? A base is a proton acceptor. 3. Discuss the relative acid strengths of H 2 O and H 2 Se, and the reasons. H 2 Se is a stronger acid than H 2 O. There are two competing factors, the electronegativity-induced electron withdrawing effect and the electronegativity-induced electrostatic interaction. H 2 O: O electronegativity-induced electron withdrawing effect weakens the bond, while strong (due to the small distance between +H and the small -O) electronegativity-induced charge-charge interaction strengthens the bond, with the bond strengthening being more dominant than the bond weakening....
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Chem 162-2011 recitation quiz II + solutions - Chem 162...

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