Chemistry*1A* MidtermExam3* April,2013* …calche/wp-content/uploads/...H Na K Rb Cl Br I....
Transcript of Chemistry*1A* MidtermExam3* April,2013* …calche/wp-content/uploads/...H Na K Rb Cl Br I....
Chemistry 1A Professor Pines
Midterm Exam 3 PRACTICE
April, 2013 # Pages, # Questions
Student Name: ______________________________ Student ID# __________________________
Potentially Useful Information
Ideal Gas: 𝑃𝑉 = 𝑛𝑅𝑇 𝑁! = 6.0221 × 10!" particles/mol Absolute T(K) = T(°C) + 273.15
𝛥𝐻!"# 𝐻!𝑂 = 40 kJ mol!! 𝐶!!! = 4.18 𝐽/𝑔!𝐶 𝑅 = 8.314J
K mol = 0.082L atmK mol
𝑣!"# = 𝑣! = !!!!!
= !!"! 𝑥 = !!± !!!!!"
!!
Particle in a 1D box:
𝐸! =!!!!
!!!!; 𝑛 = 1, 2, 3,…
∆𝑈 = 𝑞 + 𝑤 ∆𝐻 = ∆𝑈 + 𝑃∆𝑉 ∆𝐺° = ∆𝐻°− 𝑇∆𝑆°
𝑤 = −𝑃!"#∆𝑉 𝑆 = 𝑘! ln𝑊 𝛥𝑆 = !"!!"
𝑘! = 1.381 × 10!!"JK
∆𝐻° = ∆𝐻!∘ 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 − ∆𝐻!∘ 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 ∆𝐺° = ∆𝐺!∘ 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 − ∆𝐺!∘ 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠
∆𝑆° = ∆𝑆!∘ 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 − ∆𝑆!∘ 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 ∆𝑆 =𝑞!"#𝑇
For reactions of the form 𝑎A+ 𝑏B → 𝑐C+ 𝑑D, 𝑄 = ! ! ! !
! ! ! !. At equilibrium, 𝑄 = 𝐾
∆𝐺° = −𝑅𝑇 ln𝐾 ∆𝐺 = ∆𝐺°+ 𝑅𝑇 ln𝑄 ln𝐾 = −∆𝐻°𝑅
1𝑇 +
∆𝑆°𝑅
𝑞 = 𝑚𝑐∆𝑇 𝑞 = 𝑚𝐿 𝑞!"# = −∆𝐻!"#
Average Bond Enthalpies (kJ/mol) H− H 436 C− C 348 C− O 360 C = 0 192 C = C 612 O− H 463 O− O 146 C ≡ C 838 H− Cl 431 O = O 497 C− H 413 C− Cl 327
𝜆𝜈 = 𝑐 𝐸!!!"!# = ℎ𝜈 𝑐 = 2.9989 × 10! 𝑚 𝑠!! ℎ = 6.62608× 10!!" 𝐽 𝑠 𝑝 = 𝑚𝑣 𝐸! =
𝑚𝑣!
2 =𝑝!
2𝑚 Only scientific calculators may be used on this exam; graphing calculators (or any calculator with a “Solve” function the capability to store ASCII/text data, etc.) are strictly prohibited. The use of unauthorized materials is considered cheating, and will result in a grade of zero on the exam. At instructor discretion, students found cheating may also be reported to the UC Berkeley Center for Student Conduct.
Chemistry 1A Midterm Exam 1 February 12, 2013 Professor Pines 5 pages total Student Name: _____________________________________ Student ID#: ________________________
Potentially Useful Information
Violet Blue Green Yellow Orange Red
400 500 600 700
Wavelength (nm)
Light: c=λν , νhEphoton = , c = 2.99792 x 108 m s-1 NA = 6.02214 x 1023 mol-1
Photoelectric Effect: 0)( ννν hhheEkin −=Φ−=− h = 6.62608 x 10-34 J s
Matter: mvp = , Ekin =mv2
2=p2
2m R = 3.28984 x 1015 Hz
Wave/Matter: ph
deBroglie =λ R∞ = hR = 2.17987 x 10-18 J
Particle 1D box: 2
22
8mLnhEn = ; n = 1, 2, 3... R∞/mole = 1312 kJ/mol
H atom, 1-electron ion: ∞""#
$%%&
'−= RnZEn 2
2
; n = 1,2,3… me = 9.10938 x 10-31 kg
Orbital Nodes: Total = n – 1, Angular = l, Radial = n – 1 – l . H Na K Rb Cl Br I . Ionization Energy [IE] (kJ/Mole) 1312 496 419 403 1251 1140 1008 . Electron Affinity [EA] (kJ/Mole) 73 53 48 47 349 325 295 .
You may verify that the IE of atomic H corresponds to UV light with a photon wavelength of 91 nm.
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1. Which of the following equilibria will shift to the left in response to a decrease in volume? A) H2(g) + Cl2(g) ↔ 2 HCl(g) B) 2 SO3(g) ↔ 2 SO2(g) + O2(g) C) N2(g) + 3 H2(g) ↔ 2 NH3(g) D) 4 Fe(s) + 3 O2(g) ↔ 2 Fe2O3(s) E) 2HI(g) ↔ H2(g) + I2(g) 2. Which intermolecular forces predominate in the condensation of mercury? A) H-‐bonding B) Dipole-‐Dipole C) Dispersion D) Ion-‐Ion E) Ion-‐Dipole 3. What is the change in the internal energy (in J) of a system that releases 1000 J of heat and does 225 J of work on the surroundings? A) -‐10,155 B) -‐1225 C) -‐775 D) 775 E) 1225 4. For an exothermic reaction, K will increase when: A) reactants are added. B) products are added. C) the volume decreases. D) the entropy of the universe increases. E) the temperature decreases. 5. A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C. If the temperature rose from 29.5°C to 69.8°C, determine the value of ΔH°comb for aniline. A) +7.81 × 103 kJ/mol B) -‐3.20 × 103 kJ/mol C) +1.71 × 103 kJ/mol D) -‐1.71 × 103 kJ/mol E) -‐7.81 × 103 kJ/mol
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6. According to the following thermochemical equation, what mass of H2O (in g) must form in order to produce 975 kJ of energy? SiO2(s) + 4 HF(g) → SiF4(g) + 2 H2O(l) ΔH°rxn = -‐184 kJ A) 68.0 g B) 102 g C) 54.1 g D) 191 g E) 95.5 g 7. Use the ΔH°f information provided to calculate ΔH°rxn for the following:
SO2Cl2 (g) + 2 H2O(l) → 2 HCl(g) + H2SO4(l) ΔH°rxn = ? ΔH°f (kJ/mol) SO2Cl2(g) -‐364 H2O(l) -‐286 HCl(g) -‐92 H2SO4(l) -‐814 A) -‐256 kJ B) +161 kJ C) -‐62 kJ D) +800. kJ E) -‐422 kJ 8. Above what temperature does the following reaction become nonspontaneous?
FeO(s) + CO(g) → CO2(g) + Fe(s) ΔH = -‐11.0 kJ; ΔS = -‐17.4 J/K A) 632 K B) 298 K C) 191 K D) This reaction is nonspontaneous at all temperatures. E) This reaction is spontaneous at all temperatures. 9. Calculate the ΔG°rxn using the following information.
2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) ΔH°f (kJ/mol) -‐207.0 91.3 33.2 -‐285.8 S°(J/mol·K) 146.0 210.8 240.1 70.0 A) -‐151 kJ B) -‐85.5 kJ C) +50.8 kJ D) +222 kJ E) -‐186 kJ
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10. Choose the statement below that is TRUE. A) K > 1, ΔG°rxn is positive. B) K < 1, ΔG°rxn is negative. C) ΔG°rxn = 0 at equilibrium. D) All of the above statements are true. E) None of the above statements are true. 11. Determine the equilibrium constant for the following reaction at 655 K.
HCN(g) + 2 H2(g) → CH3NH2(g) ΔH° = -‐158 kJ; ΔS°= -‐219.9 J/K A) 3.99 × 1012 B) 13.0 C) 2.51 × 10-‐13 D) 3.26 × 10-‐12 E) 3.07 × 1011 12. Consider the following reaction at 175 K: 2NO(g) + O2(g) ↔ 2NO2(g) If the initial pressure of NO is 522 Torr, the initial pressure of oxygen is 421 Torr, and the total pressure at equilibrium is 748 Torr, what is Kp? A) 1.26 atm-‐1 B) 0.793 atm-‐1 C) 3.40 x 10-‐3 atm-‐1 D) 29.3 atm-‐1 E) 3.83 x 104 atm-‐1 13. Consider the following reaction:
CO2(g) + C(graphite) ↔ 2 CO(g) A reaction mixture initially contains 0.56 atm CO2 and 0.32 atm CO. Determine the equilibrium pressure of CO if Kp for the reaction at this temperature is 2.25 atm. A) 0.83 atm B) 0.31 atm C) 0.26 atm D) 0.58 atm E) 0.42 atm
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14. The gaseous reaction N! 𝑔 + 3H! 𝑔 ↔ 2NH! 𝑔 at equilibrium, when the number of moles is suddenly doubled (i.e., the total pressure is doubled). Which is true of the reaction quotient Q relative to the equilibrium constant K at the instant that the volume changes?
A) 𝑄 = !!𝐾
B) 𝑄 = !!𝐾
C) 𝑄 = 𝐾 D) 𝑄 = 2𝐾 E) 𝑄 = 4𝐾 15. Which of the following plots depicts the titration of 1M NaOH (strong base) with 1M HCl (strong acid)?
16. The hydrogenation reactions of acetylene to ethylene, C!H! + H! → C!H!, and ethylene to ethane, C!H! + H! → C!H!, are both exothermic. The heat of which reaction is greatest? A) Combustion of C2H2 B) Combustion of C2H4 C) Combustion of C2H6 D) Hydrogenation of C2H2 E) Hydrogenation of C2H4 17. Which process is accompanied by the smallest (non-‐zero) increase in entropy?
A) 1 → 2 B) 1 → 3 C) 2 → 6 D) 3 → 4 E) 5 → 6
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18. At 25°C N2O4 breaks into two NO2 molecules according to the reaction
N!O! 𝑔 ↔ 2NO! 𝑔 Which of the following could be a plot of ΔG0 vs. T for this reaction?
19. What is the pH of a 0.05 M solution of HCl? A) 0.05 B) 1.0 C) 1.3 D) 3.0 E) 7.0 20. Upon dissolution in water, a molecule A2B4 dissociates into molecules of A and B according to
A!B!(𝑎𝑞) ↔ 2AB!(𝑎𝑞)
with Keq = 2. What is the equilibrium concentration of molecule AB2 after one mole of A2B4 is added to 1.0 L of water? A) -‐1.0M B) 0.1 M C) 0.5 M D) 1.0 M E) 2.0 M