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Unformatted text preview: Version 158 – Exam 1 – Holcombe – (52460) 1 This printout should have 35 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. Helpful constants and conversions 1 atm = 760 torr = 760 mm Hg 0 degC = 273.15 K R = 8.314 J/K*mol R = 0.082 L*atm/K*mol 001 10.0 points Given that CO 2 (g) reacts with C(s) via the reaction C(s) + CO 2 (g) ⇀ ↽ 2 CO(g) and K p = 1.90 atm, what is the equilibrium partial pressure of CO 2 if 1.00 atm of CO 2 is placed in a vessel with PURE SOLID CAR BON? (Note: There was no CO initially.) 1. 0.55 atm 2. 0.43 atm 3. 0.51 atm correct 4. 0.85 atm 5. 0.60 atm Explanation: K p = 1 . 9 atm C(s) + CO 2 (g) ⇀ ↽ 2 CO(g) ini, atm 1 Δ, atm x 2 x eq, atm 1 x 2 x K p = P 2 CO P CO 2 = 1 . 9 (2 x ) 2 1 x = 1 . 9 4 x 2 + 1 . 9 x 1 . 9 = 0 Therefore x = 1 . 9 ± radicalbig (1 . 9) 2 + 16(1 . 9) 8 = 0 . 491476 P CO 2 = 1 x = 0 . 508524 atm 002 10.0 points The chemical reaction 2 H 2 O + energy → 2 H 2 + O 2 is 1. an ionic reaction. 2. a synthesis reaction. 3. an exothermic reaction. 4. an endothermic reaction. correct Explanation: Energy is required to start the reaction. 003 10.0 points Catalase (a liver enzyme) dissolves in water. A 14 mL solution containing 0 . 166 g of cata lase exhibits an osmotic pressure of 1 . 2 Torr at 20 ◦ C. What is the molar mass of catalase? 1. 2 . 3 × 10 5 g / mol 2. 1 . 58 × 10 5 g / mol 3. 1 . 81 × 10 5 g / mol correct 4. 1 . 4 × 10 5 g / mol 5. 3 . 16 × 10 5 g / mol 6. 2 . 53 × 10 5 g / mol Explanation: V = 14 mL = 0 . 014 L m = 0 . 166 g T = 20 ◦ C + 273 = 293 K Π = 1 . 2 Torr R = 0 . 08206 L · atm / K / mol Π = n RT V = m MW RT V M = mRT V Π MW = (0 . 166 g) (0 . 08206 L · atm / K / mol) (0 . 014 L)(1 . 2 Torr) × (293 K) parenleftbigg 760 Torr 1 atm parenrightbigg = 1 . 80556 × 10 5 g / mol . Version 158 – Exam 1 – Holcombe – (52460) 2 004 10.0 points Consider the temperature composition dia grams of two different binary mixtures, but each containing A as one of the compo nents. Which curve best describes the sit uation where the more volatile component of the mixture CAN be initially collected in the pure form in the distillate if X A in the boiling pot = 0.5? 1. Neither diagram 2. . 2 . 4 . 6 . 8 1 . 20 40 60 80 100 120 140 X A boilingtemperature( ◦ C) correct 3. . 2 . 4 . 6 . 8 1 . 20 40 60 80 100 120 140 X A boilingtemperature( ◦ C) Explanation: 005 10.0 points What mass of ethylene glycol ((CH 2 OH) 2 with molecular weight 62 g/mol) must be added to 1.00 L of H 2 O (of mass 1 kg) to lower the freezing point to 5 ◦ C? K f H 2 O = 1 . 86 ◦ C /m . 1. 66 g 2. 167 g correct 3. 25 g 4. 330 g 5. 123 g Explanation: MW CH 2 OH = 62 g/mol V H 2 O = 1 L m H 2 O = 1 kg T f = 5 ◦ C T f = T f Δ T f Δ T f = T f T f = 0 . 00 ◦ C ( 5 ◦ C) = 5 ◦ C Δ T f = K f · m m = Δ T f K f = 5 ◦ C 1 . 86 ◦ C /m = 2 . 688 m m = n (CH 2 OH) 2 kg water = g (CH 2 OH) 2 MW (CH 2 OH) 2 kg water...
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This note was uploaded on 09/26/2010 for the course CH 53215 taught by Professor Mccord during the Spring '09 term at University of Texas.
 Spring '09
 McCord

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