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2 The table to the right gives the experimental data for the reaction: 3A(g) + B(g) 2C(g) at 600 K for problems ) What is the order of the reaction with respect to A? A. 0 B. 0.5 C. 1 D. 2 E. 3 2) What is the order of the reaction with respect to B? A. 0 B. 0.5 C. 1 D. 2 E. 3 3) What is the rate constant? A. 4.6 s -1 M -1 B. 4.6 s -1 M -2 C. 2.9 s -1 M -1 D. 2.9 s -1 M -2 E. None of the above 4) Consider the following balanced chemical equation: Run [A] (M) [B] (M) Rate (M/s) ( ) ( ) ( )! ( ) + 2 ( ) HO aq I aq H aq I aq HO l In the first 8.0 seconds of the reaction the iodide ion, I -, concentration dropped from 0.60 M to 0.20 M. What is the rate of change in the concentration of H + + [ H ], that is, during t this time interval? A Ms -1 B Ms -1 C Ms -1 D Ms -1 E. -13 Ms -1

3 5) The natural log of the reactant concentration is plotted versus time and produces a straight line. What is the order of the reaction? A. 0 B. ½ C. 1 D. 2 E. 3 6) What is the rate constant? A. 0.5 M min -1 B. 0.5 min -1 C. 2.0 min -1 D. 2.0 M min -1 E. 2.0 M -1 min -1 Ln(Reactant Conc.) x Questions Time (min) 7) At a certain temperature, the decomposition of B is first order with a half life of 0.11 hrs. If the initial concentration of D is 0.43 M, what is its concentration after 250 seconds? A. 0 M B M C M D M E. None of the above 8) The reaction: 2A + B C has the following proposed mechanism: Step 1: A + B D (fast equilibrium) Step 2: D + B E (very slow) Step 3: E + A C + B (slow) The rate of formation of C should equal (k may be a combination of rate constants): A. k[a] B. k[a] 2 [B] C. k[a]2[b]2 D. k[a][b] E. k[a][b]2

4 9) The rate constant for a reaction increases from 10.0 s -1 to 100. s -1 when the temperature is increased from 300 K to 400 K. What is the activation energy for the reaction? A kj/mol B kj/mol C kj/mol D kj/mol E kj/mol 10) Which of the acids in the table is the strongest acid? a. Acetic b. Fluoroacetic c. Formic d. Hydrocyanic e. Hydrofluoric 11) 14 g HNO 3 is diluted to 250 ml. What is the ph? a b c d e ) A 200 ml solution consists of M HBr and M HI? What is the ph? a b c d e ) 50.0 ml of 0.50 M HCN is mixed with 50. ml of 0.20 M HCl? What is the ph? a b c d e. 1.00

5 14) 75.0 ml of 0.60 M HI is mixed with 200. ml of 0.40 M NaOH. What is the ph? a b c d e ) A M solution of a weak acid, HB, has a ph of 5.35? What is K a? a. 1.4x10-5 M b. 4.5x10-6 M c. 6.1x10-11 M d. 4.5 x10-10 M e. 1.4x10-11 M 16) Which of the following ions is acidic? a. Fe d. SO 4 b. Cl - e. Na + c. CN - 17) A 150 ml solution has 0.95 M HCN and 0.15 M NaCN. What is the ph? K a = 4.8 x a b c d e. 8.92

6 18) 20 ml 1.0 MHCl is added to a 100 ml solution of 0.40 M acetic acid, CH 3 COOH, and 0.30 M a b c d e sodium acetate, NaCH 3 COO. What is the equilibrium ph? pk a = ) What happens to the equilibrium percent dissociation of acetic acid as sodium hydroxide is added to a solution of acetic acid. (The fraction dissociated = acetate ion conc./initial acid conc.) CH 3 COOH(aq) + H 2 O(aq)! H 3 O + (aq) + CH 3 COO - (aq) a. No change b. Increases c. Decreases d. It cannot be determined 20) Buffers neutralize both acids and bases. When HNO 3 is added to a buffer solution consisting of lithium formate (LiF) and formic acid (HF), which reaction (when completed) shows the neutralization of the acid? a. H + (aq) + NO 3 (aq) b. H + (aq) +Li + (aq) c. H + (aq) +HF(aq) d. H + (aq) +F - (aq) e. H + (aq) +H 2 O(l) 21) A M -2 B M -2 C. 6.8 M -2 D. 20. M -2 E. 59 M -2 ( ) + ( )! ( ) Consider the following balanced equation: S s 3 F g SF g. 7.0 moles of sulfur are mixed 2 6 with 15 moles of fluorine in a 20.0 L container. Suppose that after 12 moles of fluorine have reacted equilibrium is established. What is K? Careful!!! c Initial Change End ( ) + 3 ( )! ( ) S s F g SF g 2 6

7 Chem 122 2nd Common Spring Mar. 5, 2012 (1/2 first common 1/2 acids) I. (a) 4pts What is the ph of a 0.65 M formic acid,hcooh? K a = 1.78 x 10-4 M. (b) 2pts What is the percent dissociation of formic acid? (c) 4pts What is the percent dissociation of 0.65 M formic acid in 0.5 M HCl? (d) 2pts Circle the correct statement and explain (a few words suffices)? No points without correct explanation. i. The percent dissociation is the same in 0.5 M HCl. Why? ii. The percent dissociation is less in 0.5 M HCl. Why?

8 Chem 122 2nd Common Spring Mar. 5, 2012 (1/2 first common 1/2 acids) Iii. The percent dissociation is more in 0.5 M HCl. Why? II. The K sp of Mg(OH) 2 is 4.6 x at 25ºC. (a1) 2PTS Write the reaction and make an ICE Table. Must label (s) or (aq). Reaction: Initial: Change: Equilibrium: (a2) 2PTS What is the solubility of Mg(OH) 2 in pure water at 25ºC in mol/l? (b) 4PTS What is the solubility of Mg(OH) 2 in a solution buffered to a ph of 7.80 at 25ºC? First, write the reaction and make an ICE Table. Reaction: Initial: Change: Equilibrium: (c) A solution contains 0.33 M Mg(NO 3 ) 2 and 0.67 M NaCl at 25ºC. At a sufficiently large hydroxide ion concentration, a precipitate is formed. What is it and at what ph does it form? 2PTS The precipitate is 2PTS The ph is

9 Chem 122 2nd Common Spring Mar. 5, 2012 (1/2 first common 1/2 acids) III. (a1) 4pts The pk a is 3.5 for the weak acid, HB. What is Q if the H = x M , 1 [ ] = HB 4.0x10 M, 3 B = 8.2x10 M? Show the reaction for full credit. ( ) H O ( aq) HB aq + 2 (a2) 2pts What happens to obtain equilibrium? Circle the correct answer for each column. For example, you could circle ai, bii, and ciii. Answers must be self-consistent for credit. Because ai. Q > K eq aii. [H + ] increases aiii. ph increases bi Q = K eq bii. [H + ] stays the same biii. ph stays the same ci. Q < K eq cii. [H + ] decreases ciii. ph decreases (b) What is the ph of 0.8 M KC 6 H 5 O? K a = 1.0 x10-10 for phenol, C 6 H 5 OH, a weak acid. 0.8 M KC 6 H 5 O means 0.8 M K + (aq) and 0.8 M CHO ( aq) 2pts First complete the reaction and the ICE table. Reaction: I C E ( ) ( ) 6 5. CHO aq + HO l! 6 5 2? 2pts K b = 2pts ph =