makeupexam1 - Version 269 – Make Up Exam 1 – VANDEN...

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Unformatted text preview: Version 269 – Make Up Exam 1 – VANDEN BOUT – (53585) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Consider the reaction 2 C 2 H 2 (g) + 5 O 2 (g) ⇀ ↽ 4 CO 2 (g) + 2 H 2 O(g) and the thermodynamic data Species Δ G f C 2 H 2 50 kcal/mol CO 2- 94 . 2 kcal/mol H 2 O- 54 . 6 kcal/mol Find K p for the reaction. Express your answer as the natural log of K p . 1. ln K p = 600 2. ln K p = 800 3. ln K p = 200 4. ln K p = 400 5. ln K p = 990 correct Explanation: Δ G = (4)(- 94 . 2) + (2)(- 54 . 6)- (2)(50 . 0)- (5)(0 . 0) kcal = (- 586 kcal)(4 . 184 kJ / kcal) =- 2451 . 824 kJ Δ G =- RT ln K p ln K p =- Δ G RT =-- 2451824 J · mol − 1 (8 . 314 J · K − 1 · mol − 1 )(298 K) = 989 . 6 002 10.0 points For gases that do not react chemically with water, the solubility of the gas in water gen- erally (decreases, increases) with an increase in the pressure of the gas and (decreases, in- creases) with increasing temperature. 1. increases; increases 2. decreases; increases 3. increases; decreases correct 4. decreases; decreases Explanation: An increase in pressure means that you have increased the concentration of gas above the solvent surface, thereby increasing the concentration of the gas in the solvent. In- creasing the temperature will decrease the solubility of the gas. 003 10.0 points Everyone should recognize that ? is a strong acid, ? is a weak acid, ? is a strong base, and ? is a salt. 1. HCl; CH 4 ; NaOH; NaCl 2. HCl; CH 3 COOH; NaOH; NaBr correct 3. HCl; H + ; NaOH; NaCl 4. HCl; H 2 SO 4 ; NaOH; NaBr 5. HNO 3 ; CH 3 COOH; NaOH; MgO Explanation: Of the answer choices, hydrochloric acid (HCl), nitric acid (HNO 3 ), and sulfuric acid (H 2 SO 4 ) are strong acids because they dis- sociate completely in water. Acetic acid (CH 3 COOH) is a weak acid due to its par- tial dissociation. Sodium hydroxide (NaOH) and magnesium oxide (MgO) are strong bases, dissociating completely to yield hydroxide (OH − ). Sodium bromide (NaBr) and sodium chloride (NaCl) are salts, compounds com- posed of a cation (metal) other than H + and an anion (non-metal) other than OH − or O 2 − . Version 269 – Make Up Exam 1 – VANDEN BOUT – (53585) 2 004 10.0 points Liquid metallic zinc (Zn) has a vapor pressure of 40 torr at 673 ◦ C and 100 torr at 736 ◦ C. Predict the normal boiling point of zinc. 1. 1452 K 2. 906 K 3. 1183 K correct 4. 1252 K 5. 1076 K Explanation: T 1 = 673 ◦ C + 273 = 946 K P 1 = 40 torr T 2 = 736 ◦ C + 273 = 1009 K P 2 = 100 torr We must first calculate Δ H vap , Zn : ln parenleftbigg P 2 P 1 parenrightbigg = Δ H vap , Zn R parenleftbigg 1 T 1- 1 T 2 parenrightbigg Δ H vap , Zn = R ln parenleftbigg P 2 P 1 parenrightbigg 1 T 1- 1 T 2 = parenleftbigg 8 . 314 J mol · K parenrightbigg ln parenleftbigg 100 torr 40 torr parenrightbigg 1 946 K- 1 1009 K = 1 . 15421 × 10 05 J / mol The normal boiling point is at 760 torr,...
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This test prep was uploaded on 04/16/2008 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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makeupexam1 - Version 269 – Make Up Exam 1 – VANDEN...

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