practice_midterm1_c_key

practice_midterm1_c_key - Name: T.A.’s name: Part A:...

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Unformatted text preview: Name: T.A.’s name: Part A: Multiple Choice —- Concepts and Calculations. Write the correct answer in the space provided on the first page. No partial credit will be given. 1. 10. ‘ - immediate result? a condensation rate decreases For the reaction H2(g) + 1/2 02(g) ——> H20(g) where AH = -241.8 k] / mol, what quantity of heat is liberated by the reaction of 10.0 L of H2 ured at 22.0 °C and 742 man? a. 120k] b. 2610kJ c. 13lOkJ d. 195 Hi e. 97.5kJ What is the work done in joules by the system when H2 expands against a constant pressure of 75 atm at 45.3 °C? The change in volume is 24.0 . a. 1.8 x 103 b. -8.2 x104 c. 8.2 x104 d. 1.8 x 105 a —1.8 x105 Compute AH for the reaction' n02(s) + CO(g) —> Mn203(s) + C02(g) a. -347.3 k] b. —46.1kJ 217.5 k] (1. —104.5 k] e. —389.1 k] An example of a fossil fuel is: a. the sun b. chlorophyll c. water d. atural gas e. carbon dioxide A 0.90 g sample of liquid water was introduced into an evacuated 2.00 L flask, which was then sealed and heated to 37 0C. What percentage, by mass, of the water remained as liquid? [Vapor pressure of wat 7 °C = 48.2 Torr] a. 10% b. 18% c. 82% 90% e. 0% Under which of the following conditions will vaporization best occur? . high mass, large surface area, high kinetic energy a weak forces between molecules, high kinetic energy, large surface area high molecular energy, small surface area d. low kinetic energy, strong molecular forces, large surface area e. small surface area, low kinetic energy, low molecular mass A liquid is in equilibrium with its vapor. If some of the vapor is allowed to escape, what is b. vaporization rate increases c. condensation rate increases (1. vaporization rate decreases 6. none of these If a substance has a heat of condensation of -1.46 kJ/g and a heat of sublimation of 4.60 kJ/g, what is its heat of solidificatio ' kJ/g? a. 4.60 - 1.46 b. -(4.60 + 1.46) c. 1.46 ~ 4.60 d. 4.60 + 1.46 e. none of these A range of melting points, a crystal that readily conducts heat and electricity and which is easily deformed but difficult to cleave, are all characteristics of what type of crystalline solid? b. ionic c. etallic d. network covalent e. peanuts a. molecular A solution component present in lesser quantity than us- vent is called a. a diluent b. an alloy c. a heterogeneous solid a solute e. a mixture 12. A solution in which the rate of crystallizati" 'h' l exceed that of solution is called: a. saturated b. unsaturated c. dilute upersaturated e. none of these 13. Which of the following is a correct statement about azeotropes? .- The components boil at distinct temperatures. o. The mixture cannot be separated by fractional distillation. c. The solution behaves as an ideal solution. (1. The vapor has a different composition than the liquid. e. The vacuum principle 14. D termine the osmotic pressure at 25 °C of an aqueous solution that is 0.028 M NaNO3. a 1.37 atm b. 0.685 atm c. 0.0729 atm d. 0.0364 atm e. 2.06 atm 15. Which of the following is not a colligative property? . freezing point depression b. boiling point elevation c. osmotic pressure @olubility e. none of these 16. How many moles of ethylene glycol must be dissolved in 500 g of water (Kf = 1.86) to lower the freezing point to —5.00 °C? a. 18.6 mol b. 2.69 mol c. 0.268 mol d. 3.73 mol® 1.34 mol 17. ose the INCORRECT statement. a. ince colloidal particles are large aggregates of atoms they are electrically neutral. . Colloidal suspensions can be prepared in which the particles do not settle. c. The addition of electrolytes to a colloidal suspension will sometimes cause the particles to coalesce and precipitate. d. Colloidal particles reflect light from a beam. e. Colloidal suspensions exhibit the Tyndall Effect. 18. Which of th '0 ing organic substances is most readily soluble in water? a. benzen yridine c. octane d. carbon tetrachloride e. toluene 19. The normal boiling point of acetone is 56.2 0C and the molar heat of vaporization is 32.0 kJ/mol. At what tempera will acetone boil under a pressure of 50.0 mmHg? a. 156 C b. 6.0 °C{ 0. 6.0 °C d. 40.7 °C e. 73.6 °C 20. ich of the following does NOT decrease rate of vaporization? a losing container lid b. increasing forces between molecules 0. increasing mass of molecule (1. decreasing temperature e. decreasing surface area 21. Two substances, A and B, are of the same mass, but A feels warmer to the touch than B. v w hich of the following is true? 6‘ A has a higher Cp than B b. B has a higher Cp than A c. A and B have equal Cp d. all of the above Name: T.A.‘s name: Part E: Short answer questions. No partial credit. 22. Circle the correct answer: a. a) Which has the lower boiling point? oil ORfitfr/ b) Which has the higher boiling point? 5mm OR hummer . . ./ c) Wlnch has a higher vapor pressure? benzene O rid d) Which liquid has a higher surface tension? carbon tetrachloride 0 chloroform. (3?“ ‘ “J e) Which has the higher boiling point? \ xencyOR argon 23. Given the phase diagram. answer the following questions. T . . fl . a) Point A represents the 5‘. “9&4 I 1A t. _- (2 words) b) The process of sublimination occurs across line i 2 . c) The supercritical region lies higher than point i. d) If a compound exists in the liquid hase, an increase in pressure along an isotherm may cause it to go into the x phase. Name: T.A.’s name: Part C: Show all work to receive or full credit. Include all state symbols for species when writing chemical equations. Also, write your answer with the correct number of significant figures. If you are unable to solve the first part of a multipart problem, then assume an answer and continue with the latter part showing all your work. 24. A solution is prepared by mixing 5.8t g of acetone and 11.9 g of chloroform. At 35 “C this solution has a total vapor pressure of 260 Torr. The vapor pressures of pure acetone and pure chloroform at 35 0C are 345 Torr and 293 Torr, respectively. wk s ‘ \O 0 “HQ, C L yes of acetone and chloroform. | E Bis A E) wast 677%) {6 b) Determine the mole fraction of acetone and chloroform. ,1“ otoo a (lg—Olly QtOQr 0mg 3". a “lit a) Determine the number of v \— om c) What is the expected vapor pressure? EM :2 WM: ‘* 'kti‘ L 2 (56‘s '(BQCQL’D) + ('19 ":3 “EHXOQQ : \Bmorl d} Compare the expected and observed vapor pressure. Is this solution idea]? If the solution is not ideal, explain the deviation. %l§51rr > abo 'EW <43 54%;] tCC’iYLhfl v9 "ht: [Gimme g . 5 WKK eta girl.va CH3 \ CH 2, MW? Name: T.A.’s name: 25. A 125 g stainless steel ball bearing (Cp 2 0.50 J / g °C) at 525 °C is dropped into 75.0 mL of water at 28.5 °C in an open Styrofoam cup. The water is brought to a boil, with the temperature rising to 100 °C. What mass of water‘vaporizes while the boiling continues? @m:\2§3 T‘ : — Mmm Aflw‘) " \8 jbuA meted/M Gages Z (2) 35520 _—~ “1‘32. ’ 50,500 Answer: Mass of water vaporized = l I A) Q» 0 0 grams Name: T.A.‘s name: 26. The element Enderilium (DrE) crystallizes in the simple cubic structure. The radius of DrE is 2.00 A. (Molar mass of DrE is 6.022 g I mol) a) How many atoms of DYE exist in a unit cell? 3 “0% (L00 L Uhtl‘ b) What is the coordination number of DrE? c) What is the mass 1.: sin-ms of DrE in one unit cell? L 0M wok he‘th ‘ ~12 03 "—‘fl if lm - We can (9.5mm \ UhithQllQ :MW d) What is the volume of a unit cell of DrE? a “)3 (R 3c \I z (10%; a8 f3 r 80“) l0 :lElECLEEl W W19? Gem e) What is the density of DrE (in units ofg s“ cm“)? :2: — M \l 4.0 RX/Uttxlullg K) W Name: T.A.’s name: Conversions: 1 atm = 760 Torr 100 cm = 1010 A 2.54 cm = 1.00 in = 101,325 Pa 11b=453.6g lcal=4.184J Constants: R=8.3145 J/molK RH=2.179x10'181 c = 2.9979 x 108 m/ s h = 6.626 x 103.4 J s g = 9.81 m/ s NA = 6.022 x 1023 atoms / mol d (H20) = 1.00 g / cm3 Cp (H20) = 4.184 I / g °C Equations: AU=q+w AH=AU+PAV PA=xAP; C=k~P 7z=iMRT n/l=dsin6 gas P2 AHvap 1 1 . . ln—= ——— ATf =~szm ATb =1Kbm q=nAH=meAT P: R 2 T2 Enthalpy Values and Reactions: AHvap (H20) = 40.6 k] / mol AHfus (H20) 2 6.01 k] / mol MnOZ (s) + CO (g) —> MnO (5) + C02 (g) AH = -150.6 k] / mol Mn304 (s) + CO (g) —> 3 MnO (5) + C02 (g) AH = - 54.4 kJ / mol 3 Mn203 (s) + CO (g) —> 2 Mn304 (s) + C02 (g) AH = -l42.3 kJ / mol Molecules: Rfl$\0 9A 5 t6 0 Q UAQXC’A, I I / CH 3CH2CHZCHZCH2CH 2CHZCH3 « \ \0 mli ertf/p benzene pyridine octane & \ r \ V 1 WQ, 6 C W l / CH3 Chbk’ig-LR/V’N Cl — C13 - Cl \ | 4 Cl carbon tetrachloride toluene C) KQNM acetone CH3COCH3 k}\L\C}\}C‘Q/‘A2 chloroform CHC13 ...
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practice_midterm1_c_key - Name: T.A.’s name: Part A:...

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