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EXAM 2 – Dr. Vedernikov Full Name: _________________________________ First letter of your Last Name : Please PRINT “ I pledge on my honor that I have not given or received any unauthorized assistance on this examination” Signature Date This exam contains 6 pages in total including this title page:  10 questions on pages 2 - 4 (do NOT separate these pages and the title page)  some physical constants on page 5,  important formulas on p. 5, and  the Periodic Table of the Elements on page 6 (you may detach it). Check if you have all of that before you begin. You may use any blank pages as a scratch paper. Put your answers ONLY in the space provided. Examination rules:  You may not begin until everyone has an exam  When time is called, put your pencil down and remain in your desk  After all exams have been collected, you will be dismissed Question 1: _____/ 12 pts Question 6: ____/ 12 pts Question 2: _____/ 8 pts Question 7: ____/ 12 pts Question 3: _____/ 12 pts Question 8: ____/ 8 pts Question 4: _____/ 12 pts Question 9: ____/ 8 pts Question 5: ____/ 10 pts Question 10: ____/ 6 pts TOTAL POINTS : _________/100

2 1. (12 pts) Consider an energy diagram for an overall reaction A + C  D ( 1 ) that involves two elementary steps: a) Which of the rate constants, k 1 , k -1 or k 2 is the smallest and which is the largest? Explain briefly. Smallest: _____ Largest: ______ b) What is the overall reaction order in [ C ]? Explain briefly. Order in [C]: ____ c) Which transition state, TS 1 or TS 2 , corresponds to the rate-determining step? Explain briefly. Answer: _____ d) Is the overall reaction (1) spontaneous or not (circle one)? Explain briefly. yes no 2. (8 pts) Use the < and/or = signs and rank the following. Assume otherwise identical conditions. a) H 2 O(l), 1M HCl(aq), 1M Na 2 HPO 4 (aq), according to their increasing ability to dissolve poorly water- soluble BaHPO 4 (s): _________________________________ b) 1M NH 3 (aq), H 2 O(l), 1M HCl(aq), according to their increasing ability to dissolve poorly water-soluble AgCl(s): _________________________________ 3. (12 pts) Consider two reactions below. For each of the reactions decide if the reaction is reactant-favored or product-favored. K a (HSO 4 - ) = 0.012, K a (H 3 PO 4 ) = 7.5×10 -3 , K a (H 2 PO 4 - ) = 6.2×10 -8 ; K a (HPO 4 2- ) = 4.2×10 -13 ; K a (H 2 CO 3 ) = 4.2×10 -7 , K a (HCO 3 - ) = 5.6×10 -11 Explain briefly. Show your work: Reaction 1 : NaHSO 4 ( aq ) + NaH 2 PO 4 ( aq )  Na 2 SO 4 ( aq ) + H 3 PO 4 ( aq ) Circle one: reactant-favored product-favored Reaction 2 : NaHCO 3 ( aq ) + NaH 2 PO 4 ( aq )  H 2 CO 3 ( aq ) + Na 2 HPO 4 ( aq ) Circle one: reactant-favored product-favored

3 4. (12 pts) Calculate the pH of 1.00 L of solution containing 0.55 mol NH 4 Cl ( pK a = 9.25) and 1.33 mol NH 3 : a) as prepared; b) after addition of 0.20 mol of NaOH( s ) to the solution. Show your work: a) pH of the solution, as prepared ______________ b) pH after addition of NaOH( s ) ______________ 5. (10 pts) Calculate pH of a 0.20 M NaCN( aq ) solution at 25 o C ( K b (CN - ) = 2.5×10 -5 ). Show your work: pH = _______ 6. (12 pts) Use the < and/or = signs and rank the following. Assume otherwise identical conditions. a) i) 35 Cl( g ) + 35 Cl( g ), ii) 36 Cl( g ) + 36 Cl( g ), iii) 37 Cl( g ) + 37 Cl( g ), according to increasing gas kinetic collision rate: lowest _________________________________highest b) H 2 S, H 2 SO 3 , H 2 SO 4 , according to increasing pK a in water: lowest __________________________ highest c) Cl - , Br - , F - , according to increasing pK b in water: lowest _________________________________highest d) Xe(g), Ar(g), Kr(g), according to increasing standard molar entropy: lowest _________________ highest 7. (12 pts) Consider the following reversible reaction: HSO 4 - ( aq ) + H 2 O( l ) SO 4 2- ( aq ) + H 3 O + ( aq )  H rxn > 0 Write the equilibrium constant expression for this reaction: K = _________________ In which direction would the equilibrium above shift upon disturbing (circle the correct answer)? a) upon dilution with pure water: left no change right b) upon increase of [HSO 4 - ]: left no change right c) upon increase of [SO 4 2- ]: left no change right d) upon increase of temperature: left no change right

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4 8. (8 pts) For the following reaction NaH 2 PO 4 ( aq ) + Na 2 S( aq ) Na 2 HPO 4 ( aq ) + NaHS( aq ) a) write a balanced net ionic equation : b) identify two conjugate acid-base pairs involved: One conjugate acid-base pair, acid: _____________, conjugate base: __________ Another conjugate acid-base pair, base: _____________, conjugate acid: __________ 9. (8 pts) Consider the following reaction used for the industrial production of H 2 (g): CH 4 (g) + H 2 O(g)  CO(g) + 3H 2 (g) Calculate the standard entropy change,  S o rxn , in J/K , and the standard enthalpy change for this reaction,  H o rxn , in kJ given the following information: ∆࠵? ௙ ௢ ሺ࠵?࠵? ସ , ࠵?ሻ = -74.6 kJ/mol ; ࠵? ௢ ሺ࠵?࠵? ସ , ࠵?ሻ = 186.3 J/K ; ∆࠵? ௙ ௢ ሺ࠵? ଶ ࠵?, ࠵?ሻ = -241.8 kJ/mol ; ࠵? ௢ ሺ࠵? ଶ ࠵?, ࠵?ሻ = 188.8 J/K ; ∆࠵? ௙ ௢ ሺ࠵?࠵?, ࠵?ሻ = -110.5 kJ/mol ; ࠵? ௢ ሺ࠵?࠵?, ࠵?ሻ = 197.7 J/K ; ࠵? ௢ ሺ࠵? ଶ , ࠵?ሻ = 130.7 J/K . Show our work: Reaction standard enthalpy,  H o rxn : ___ _________ kJ sign magnitude Reaction standard entropy,  S o rxn : ___ _________ kJ sign magnitude 10. (6 pts) Consider another reaction used for the production of H 2 (g): CO(g) + H 2 O(g)  CO 2 (g) + H 2 (g) . Find the equilibrium constant K C for the reaction at 700.0 o C given the following information: ∆࠵? ௥௫௡ ௢ = -41.2 kJ ; ∆࠵? ௥௫௡ ௢ = -42.0 J/K . Show our work: Reaction equilibrium constant, K C , at 700.0 o C _________

5 Some Physical Constants and conversion factors Gas constant, R = 0.08206 L×atm/(mol×K) = 8.314 J /(mol×K) Important formulas The reduced mass of particles 1 and 2 : ࠵? ࠵?࠵? ൌ ࠵? ࠵? ࠵? ࠵? ࠵? ࠵? ା࠵? ࠵? , kg/mol The average relative speed of particles 1 and 2 : ࠵? ࠵?࠵?࠵? തതതതത ൌ ට ࠵?࠵?࠵? ࠵?࠵? ࠵?࠵? , m/s The kinetic collision rate constant of particles 1 and 2 : ࠵? ൌ ࠵?࠵? ࠵? ࠵?ሺ࠵? ࠵? ൅ ࠵? ࠵? ሻ ࠵? ࠵? ࠵?࠵?࠵? തതതതത ࠵?࠵?࠵? ቀ ି࠵? ࠵? ࠵?࠵? ቁ ൈ ࠵?࠵? ࠵? ሺ࠵?/࠵? ࠵? ሻ , ࠵? ࠵?࠵?࠵? ିଵ ࠵? ିଵ Equilibrium constant K C for reaction a A + b B  c C + d D : ࠵? ࠵? ൌ ሾ࠵?ሿ @࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵? ሾ࠵?ሿ @࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵? ሾ࠵?ሿ @࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵? ሾ࠵?ሿ @࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵? ሺ࠵?ሻ ࠵?ା࠵?ି࠵?ି࠵? Relationship between K C and K P values for reaction a A( g ) + b B( g )  c C( g ) + d D( g ) : ࠵? ࠵? ൌ ሾ࠵?ሿ ࠵? ሾ࠵?ሿ ࠵? ሾ࠵?ሿ ࠵? ሾ࠵?ሿ ࠵? ൌ ࠵? ࠵? ሺ࠵?࠵?ሻ ࠵?ା࠵?ି࠵?ି࠵? Reaction quotient Q C f or a reversible reaction a A + b B  c C + d D : ࠵? ࠵? ൌ ሾ࠵?ሿ ࠵? ሾ࠵?ሿ ࠵? ሾ࠵?ሿ ࠵? ሾ࠵?ሿ ࠵? ሺ࠵?ሻ ࠵?ା࠵?ି࠵?ି࠵? pK a and pK b scales: pK a = - logK a ; pK b = - logK b ; pK a (HA) + pK b (A - ) = 14.00 in water at 25 o C pH and pOH scales: pH = - log[H + ] ; pOH = - log[OH - ] ; pH + pOH = 14.00 in water at 25 o C The Henderson-Hasselbach equation: ࠵?࠵? ൌ ࠵?࠵? ࠵? ሺ࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?ሻ ൅ ࠵?࠵?࠵? ቀ ሾ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?ሿ ࠵? ሾ࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?ሿ ࠵? ቁ Molar solubility of an ionic compound M a X b : ට ࠵? ࠵?࠵? ࠵? ࠵? ࠵? ࠵? ࠵?శ࠵? Entropy change for a phase transition: ∆࠵? ࠵?࠵?࠵? ൌ ∆࠵? ࠵?࠵?࠵? ࠵? ࠵?࠵?࠵? ; ∆࠵? ࠵?࠵?࠵? ൌ െ ∆࠵? ࠵?࠵?࠵? ࠵? ࠵?࠵?࠵? The standard Gibbs energy change of a reaction: ∆࠵? ࠵?࠵?࠵? ࠵? ൌ ∑ ࠵? ࠵? ∆࠵? ࠵? ࠵? ሺ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?ሻ െ ∑ ࠵? ࠵? ࠵? ࠵? ࠵? ሺ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?ሻ A non-standard Gibbs energy change of a reaction: ∆࠵? ࠵?࠵?࠵? ൌ ∆࠵? ࠵?࠵?࠵? ࠵? ൅ ࠵?࠵?࠵?࠵?࠵? A Gibbs energy change for the system: ∆࠵? ࠵?࠵?࠵? ൌ ∆࠵? ࠵?࠵?࠵? െ ࠵?∆࠵? ࠵?࠵?࠵? A reaction standard Gibbs energy and equilibrium constant:  G o = -RTln ( K ) The van’t Hoff’s equation: ࠵?࠵?ሺ࠵?ሻ ൌ െ ∆࠵? ࠵? ࠵?࠵? ൅ ∆࠵? ࠵? ࠵? Standard entropy change of a reaction: ∆࠵? ࠵?࠵?࠵? ࠵? ൌ ∑ ࠵? ࠵? ࠵?°ሺ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?ሻ െ ∑ ࠵? ࠵? ࠵?°ሺ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?ሻ

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6 Periodic Table of the Elements MAIN-GROUP ELEMENTS MAIN-GROUP ELEMENTS 1 18 1 1 H 1.008 2 13 14 15 16 17 2 He 4.003 2 3 Li 6.941 4 Be 9.012 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 9 F 19.00 10 Ne 20.18 d-BLOCK ELEMENTS 3 11 Na 22.99 12 Mg 24.31 3 4 5 6 7 8 9 10 11 12 13 Al 26.98 14 Si 28.09 15 P 30.98 16 S 32.07 17 Cl 35.45 18 Ar 39.95 4 19 K 39.10 20 Ca 40.08 21 Sc 44.96 22 Ti 47.87 23 V 50.94 24 Cr 52.00 25 Mn 54.94 26 Fe 55.85 27 Co 58.93 28 Ni 58.69 29 Cu 63.55 30 Zn 65.41 31 Ga 69.72 32 Ge 72.61 33 As 74.92 34 Se 78.96 35 Br 79.90 36 Kr 83.80 5 37 Rb 85.47 38 Sr 87.62 39 Y 88.91 40 Zr 91.22 41 Nb 92.91 42 Mo 95.94 43 Tc (97.9) 44 Ru 101.1 45 Rh 102.9 46 Pd 106.4 47 Ag 107.9 48 Cd 112.4 49 In 114.8 50 Sn 118.7 51 Sb 121.8 52 Te 127.6 53 I 126.9 54 Xe 131.3 6 55 Cs 132.9 56 Ba 137.3 57-71 72 Hf 178.5 73 Ta 180.9 74 W 183.8 75 Re 186.2 76 Os 190.2 77 Ir 192.2 78 Pt 195.1 79 Au 197.0 80 Hg 200.6 81 Tl 204.4 82 Pb 207.2 83 Bi 209.0 84 Po ( 209.0 ) 85 At ( 210.0 ) 86 Rn ( 222.0 ) 7 87 Fr ( 223.0 ) 88 Ra ( 226.0 ) 89-103 104 Rf (261.1) 105 Db (262.1) 106 Sg (263.1) 107 Bh (262.1) 108 Hs (265) 109 Mt (266) 110 Ds (271) 111 Rg (272) 112 Cn (285) 113 Nh (284) 114 Fl (289) 115 Mc (288) 116 Lv (292) 117 Ts (294) 118 Og (294) LANTHANIDES AND ACTINIDES 6 Lanthanides 57 La 138.9 58 Ce 140.1 59 Pr 140.9 60 Nd 144.2 61 Pm ( 144.9 ) 62 Sm 150.4 63 Eu 152.0 64 Gd 157.3 65 Tb 158.9 66 Dy 162.5 67 Ho 164.9 68 Er 167.3 69 Tm 168.9 70 Yb 173.0 71 Lu 174.0 7 Actinides 89 Ac ( 227.0 ) 90 Th 232.0 91 Pa 231.0 92 U 238.0 93 Np ( 237.1 ) 94 Pu ( 244.1 ) 95 Am ( 243.1 ) 96 Cm ( 247.1 ) 97 Bk ( 247.1 ) 98 Cf ( 251.1 ) 99 Es ( 252.1 ) 100 Fm ( 257.1 ) 101 Md ( 258.1 ) 102 No (259.1) 103 Lr (260.1)