2004 Exam 2

# 2004 Exam 2 - CHE132 Midterm 2 Form 0 CHE132 Midterm 2...

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CHE132 Midterm 2 Form 0 1 CHE132 Midterm 2 Spring 2004 Form 0 There are 20 multiple choice questions each worth 5 points. The entire exam counts 100 points toward your course total. Question 21 is a bonus question worth 5 points, so you actually have 21 opportunities rather than 20 to earn a perfect 100 points. Constants The Gas constant = R = 8.314 J mol -1 K -1 The Gas constant = R = 0.08206 L atm mol -1 K -1 The molar mass of water is 18.02 g mol -1 The density of liquid water is 1 g/mL. 1 atm = 1.013 x 10 5 Pa. 1 cm 3 = 1 x10 -3 L = 1 x 10 -6 m 3 Equations For a first order reaction: ln([A] o /[A]) = kt t 1/2 = ln2/k For a second order reaction: 1/[A] – 1/[A] o = kt reaction = Σ coeff p f (products) - Σ coeff r f (reactants) G° = -RTlnK eq lnK eq = - H°/RT + S°/R G reaction = reaction + RTlnQ k = Ae -Ea/RT lnk = lnA – (E a /RT) E R k k TT a = F H G I K J F H G I K J ln 2 1 12 11 pH = -log[H 3 O + ] K w = [H 3 O + ] eq [OH - ] eq = 1 x 10 -14 For a weak acid HA that dissociates into A - and H 3 O + in aqueous solution: K a = [H 3 O + ] eq [A - ] eq / [HA] eq Quadratic Equation ax 2 + bx + c = 0 x bb a a = −± 2 4 2 c

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CHE132 Midterm 2 Form 0 2 Question 1. The rate law for a reaction is: Rate = k[A] 1 [B] 2 Which one of the following statements is not correct. A: The reaction is first order in A. B: The reaction is second order in B. C: k is the rate constant for the reaction. D: The rate is equally sensitive to changes in the concentration of A and B. E: A change in the concentration of B will have a greater effect on the rate than an identical change in the concentration of A. Question 2. The pH of a 0.5 M solution of an acid HA is 4.7. Calculate the acid dissociation constant K a for the acid. HA(aq) + H 2 O(l) H 3 O + (aq) + A - (aq). A: 2.0 x 10 -5 B: 4.0 x 10 -10 C: 8.0 x 10 -10 D: 5.0 x 10 9 E: 4.7 [H 3 O + ] = 10 -4.7 = 2 x 10 -5 . K eq = [H 3 O + ][A - ] / [HA] = (2 x 10 -5 ) 2 / (0.5- 2x10 -5 ) = 8.0 x 10 -10 Question 3. The equilibrium constant for the dissociation of diatomic fluorine F 2 (g) into fluorine atoms F(g) is K eq = 2.1 x 10 -22 . F 2 (g) 2F(g) Which one of the following statements is correct ? A: At equilibrium a sample of fluorine consists almost entirely of fluorine atoms F(g). B: At equilibrium a sample of fluorine consists of equal concentrations of F 2 (g) and F(g). C: At equilibrium [F]/[F 2 ] = 2. D: At equilibrium [F]/F 2 ] = 0.5. E: At equilibrium a sample of fluorine consists almost entirely of diatomic fluorine F 2 (g).
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2004 Exam 2 - CHE132 Midterm 2 Form 0 CHE132 Midterm 2...

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