Chemistry+exam+review[1]25Nov09

Chemistry+exam+review[1]25Nov09 - 1. Which of the following...

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1. Which of the following statements is true regarding the impact of additional chemicals on the solubility of a saturated solution of CaCO 3 ? A) CaCl 2 will decrease its solubility; NaOH will increase its solubility. B) HCl will decrease its solubility; CaCl 2 will increase its solubility. C) CaCl 2 will decrease its solubility; HCl will increase its solubility. D) NaCl will decrease its solubility; HCl will increase its solubility. The solubility of CaCO 3 is given by the equation: CaCO 3 Ca+2 + CO 3 -2 CaCl 2 will decrease the solubility due to common ion effect, while HCl will increase the solubility since H + will react with CO 3 -2 hence causing the equilibrium to shift to the right; that is: more CaCO 3 will dissolve.) 2. For the following reaction: Ag 2 O (s) → Ag (s) + ½O 2 (g) H°f (kJ / K . mole) -31 0 0 S° (J / K . mole) 121.3 42.6 205.1 Calculate Kp at 25 °C. A) 2.22 x 10 -3 B) 2.22 x 10 -2 C) 1.09 x 10 -2 D) 4.41 x 10 -1 Solution: Ag2O 2Ag + 1/2O 2 ∆H = ∑nH of products - ∑nH of reactants ∆H = 0 – [1(-31 kJ/mol.K)] ∆H = 31 kJ/mol.K ∆H = 31,000 J/mol.k
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∆S = ∑nS of products - ∑nS of reactants ∆S = [2(42.6) + ½(205.1)] – [(1)(121.3)] ∆S = 66.45 J/mol.K ∆G = ∆H - T∆S ∆G = 31000J/mol.K – (298.15K)(66.45J/mol.K) ∆G = 11,187.93 J/mol ∆G = -RT ln K 11,187.93 J/mol = -8.314 J/mol.K (298.15K) ln K ln K = -4.51 K = 1.09 x 10 -2 3. For the following reaction: Ag 2 O (s) → Ag (s) + ½O 2 (g) H°f (kJ / K . mole) -31 0 0 S° (J / K . mole) 121.3 42.6 205.1 Calculate the temperature (°C) where K p = 1. A) 152 B) 194 C) 222 D) 367 Using data from #10, input values in the formula:
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-2 - 31,000 J/mol/ 8.314 J/molK] (1/T2 – 1/298) 4.52 = -3728.65 (1/T2 – 0.00336) 1/T2 = 0.00215 T2 = 466.47 K In Celsius: 0 C = 466.47 K – 273 = 193.47 (This answer is near to 194) 4. The equilibrium constant for a reaction is 0.50 at 30°C. What is the value of ΔG° (kJ/mol) at this temperature? A) -4.1 B) 4.1 C) 1.4 × 10 2 D) 1.7 E) More information is needed. ΔG° = -RT ln K ΔG° = - 8.314 J/mol K (303 K) ln 0.5 ΔG° = 1,746.14 J/mol ΔG° = 1.75 kJ/mol 5. Given the thermodynamic data in the table below, calculate the equilibrium constant for the reaction: 2SO 2 (g) + O 2 → (g) 2SO 3 (g) Substance ΔHf° (kJ/mol) ΔS° (J/mol K) SO 2 (g) -297 249
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This note was uploaded on 02/06/2011 for the course CHEM 115L taught by Professor Nakkiew,pichaya during the Spring '10 term at Grand Canyon.

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Chemistry+exam+review[1]25Nov09 - 1. Which of the following...

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