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# solutionexam2_pdf - Version 425 – Exam 2 – Sutcliffe...

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Unformatted text preview: Version 425 – Exam 2 – Sutcliffe – (52410) 1 This print-out should have 28 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Consider the equilibrium 2 SO 2 (g) + O 2 (g) ⇀ ↽ 2 SO 3 (g) What happens to the partial pressure of SO 3 when the partial pressure of SO 2 is de- creased? 1. Unable to determine 2. remains the same 3. increases 4. decreases correct Explanation: The partial pressure of SO 3 will decrease when the partial pressure of SO 2 is decreased. According to Le Chatelier’s principle, a de- crease in the partial pressure of a reactant will shift the equilibrium to the left, decreas- ing the partial pressure of the products, in this case SO 3 . 002 10.0 points Assume the solute is a NONelectrolyte. How many moles of CO(NH 2 ) 2 are present in 135 g of water, if the freezing point of the solution is- 4 . 02 ◦ C? k f (water) = 1 . 86 K · kg / mol. 1. . 27 mol 2. . 292 mol correct 3. . 303 mol 4. None of these 5. . 324 mol 6. . 281 mol Explanation: k f = 1 . 86 K · kg / mol Δ T f =- 4 . 02 ◦ C = 4 . 02 K m solvent = 135 g = 0 . 135 kg Δ T f = k f m = k f n CO(NH 2 ) 2 m solvent n CO(NH 2 ) 2 = Δ T f m solvent k f = (4 . 02 K) (0 . 135 kg) 1 . 86 K · kg / mol = 0 . 291774 mol . 003 10.0 points Which solution is the most acidic? 1. one with pH = 3 2. one with [OH − ] = 10 − 12 M correct 3. . 0001 M HI (strong acid) 4. one with [H 3 O + ] = 10 − 5 M Explanation: pH = 3, so [H 3 O] = 10 − pH = 10 − 3 M The strong acid HI completely disassoci- ates in aqueous solution to produce [H 3 O + ] = 10 − 4 M [OH − ] = 10 − 12 M, so [H 3 O + ] = K w [OH − ] = 10 − 14 10 − 12 = 10 − 2 M The most acidic solution has the highest [H 3 O] value. 004 10.0 points What is the osmotic pressure of a solution that contains 3 . 42 × 10 − 3 moles of lactose in 192 mL of solution at 24 ◦ C? 1. 329 . 934 torr correct 2. 26 torr 3. 434 torr 4. 5 torr Version 425 – Exam 2 – Sutcliffe – (52410) 2 5. 25 torr Explanation: n = 3 . 42 × 10 − 3 mol V = 192 mL T = 24 ◦ C + 273 = 297 K π = M RT = mol lactose L soln RT = 3 . 42 × 10 − 3 mol lactose . 1 L soln × . 08206 L · atm mol · K × 297 K × 760 torr 1 atm = 329 . 934 torr 005 10.0 points Consider the reaction A + B ⇀ ↽ C + D K c = 33 . 587 . What is the K c value for the reaction 2 A + 2 B ⇀ ↽ 2 C + 2 D ? 1. . 0298 2. 1130 correct 3. 33 . 587 4. 5. 67 . 174 Explanation: 006 10.0 points According to the Bronsted-Lowry concept of acids and bases, which of the following state- ments about a base is NOT true? 1. A base must contain a hydroxide group. correct 2. A base will share one of its electron pairs to bind H + ....
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solutionexam2_pdf - Version 425 – Exam 2 – Sutcliffe...

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