ch1020_2008b_finalexamsolns

ch1020_2008b_finalexamsolns - MacDonald. C HM I 020, Final...

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Unformatted text preview: MacDonald. C HM I 020, Final Exam Name: 50 /£) 74/ .014 j Score: "" /75 Consider the graph below for questions 1-3. “m ungceu H vaporProsmtlom a s ’2‘ § § 0 E 40 BO 80 100 “meme (°Cl 1. Which compound has the highest boiling point at standard atmospheric pressure? [2 ptsl Ci-ICI3 CC]4 2. Which compound has the weakest intermolecular forces between the molecules? |2 ptsl ccu H20 Which compound has no molecular dipole? [2 ptsl CHCI3 H20 4. Which structure ABA (left side) or ABC (right side) represents a hexagonal closest packed (bcp) structure? Circle your answer. [2 ptsl w ABA (lcl‘t side) ABC (right side) VSEPR theory provides a useful tool to predict the shapes of covalent molecules. Which statement describes the basic principle of VSEPR theory? |2 ptsl U] a. Re ulsion between atomic nuclei hel 5 determines the sha es ol‘ molecul b. Re ulsion between e ectrons in covalent bonds and [one pairs determines the shapes of molecules. c. Repulsion between a centra a om an on e pertpieral atoms determines t e srap . ' ' ecu es. (1. Repulsion between electrons in covalent bonds but not lone pairs determines the shapes of molecules. 6. Circle the picture that represents the orbital(s) on an slag-hybridized carbon atom. l2 ptsl 5% @ 7. Sodium hydroxide (NaOH) pellets dissolve readily in water at room temperature to form a solution that becomes hot to the touch. Which one of the following statements is true. [2 ptsl a. The energy required to separate Na* and 'OH ions is greater than the energy released when the ions dissolve. b. The attractive forces between molecules of water is greater than those between Na‘- and ‘OH ions. c. Dssolving NaOH in water is an endothermic recess. (1. Solvation of Na+ and ‘OH ions by molecules of water releases more energy than the energy required to separate Na' and 'OH ions. 8. Which one of the following substances l'orms an ionic solid? I2 pts] SiN 51‘}, (‘JH u:- MacDonald. C HM! 020. Final Exam 9. A molecule of carbon monoxide, CO, has what bond order? [2 pts] 0 l 2 CD 4 10. Which one of the following decreases as the strength of attractive intermolecular forces increases? [2 ptsl a. The heat of vaporization of a liquid. c. The sublimation tcmerature of a solid. b. The normal boiling point of a liquid. d. The vapor pressure ofa liquid. 1 l . If the temperature of a gas is increased holding the volume constant, the pressure of the gas increases because: |2 ptsl ., a. The pressure of the gas must be equal to the barometric pressure. b ' - fthe contai r less frequently. (1. The strength of the intermolecu ar attractions increases. I- ll.‘ ‘ . I‘ l2. a. Consider the phase diagram for H30 below. At the conditions of pressur‘ and temperature at point A, H30 will be in what phase? [2 ptsl a liquid Pressure (torr) both a solid & a liquid 100 Temperature ("0) b. Starting at point A. if the pressure is increased steadily while holding temperature constant. the phase of H30 will change from: l2 ptsl gas to solid gas to liquid liquid to solid I3. The crystal packing of sodium chloride (NaCI), or table salt, is shown below. In what type of cubic packing arrangement docs NaCI crystallize"? Circle your answer. [2 ptsl NaCl unit cell simple cubic body-centered cubic Cl‘ My ‘ her °""J NJ e Nam unit con 14. For which gas do the molecules have the lowest average velocity? |2 ptsl He CH.I NH3 l5. Which compound is polar‘.J I2 ptsl er. cs2 striu 16. A molecule with formula AX: uses what type oi" hybrid orbitals to form its bontls‘.’ I2 pts] 3 . ‘ . ’v . ‘ 3 sp sp sp Li sp d Is.) MacDonald, CHMIOZO, F inal Exam 1?. a. Vanillin is a major component of Oil of Vanilla. How many pi (n) bonds does a molecule of vanillin contain? [2 pts] 00Ha “£00” 1 n bonds 2 3|: bonds 3 717 bonds 5 7E bonds b. What are the bond angles on the carbon atom in the carbonyl group (C=O) marked by the arrow? [2 pts] 90° 109° 180° 18. The unit cell for nickel arsenide is shown below The arsenic atoms are located inside the unit cell. What is the formula for this compound? [5 pts] A's =7 2- ‘95"“ Na}. A5, _ 6* a.“ cow/+4“ M ‘2' "‘4 MA: at: .r‘: 597% 42/3905 19. How much heat in joules is required to convert 25 .0 g of ice at 0 “G into liquid water at 30 CC? The enthalpy of fusion (AHMM) for melting ice is 6.02 kJ/rnol, the specific heat capacity of water is 4.18 JIg°C and the molar mass of H20 is 18.0 g/mol. [5 pts] formula = [ca—5 Mari—cw: m g (0203' .. 2.5.?- (lg§)< Mo] - I u’a—+"P 4—1” 02—9 («IA—4L” #302: 2.523}. (3452-02) a: 3/355" 737L~/ W4! Eut‘U‘mJ: V30 T+ 3135‘T= 11724 5‘ heat required: {I 1, é J 20. Carbon dioxide gas (C02) commonly is used in fire extinguishers because it is heavier than air and retards combustion by displacing oxygen. Calculate the density (d) of C02 (44.0 g/mol) in g/L at 30°C at 820 torr. [5 pts] d = MP = (fancy/ml) (£10 +»»»)( athwl I)! A. RT (o.or.:o££“.:fifl)(3°°c_r 273a ‘ / moi-K density = A g/L MacDonald. CHM1020, F inal Exam 21. How much energy is released in it] when 24.0 g of methane gas, CH4 (16.0 g/mol), are burned in the presence of oxygen (02)? Combustion of methane occurs according to the reaction below. [5 pts] CH4 (g) + 2 02 (g) —> (:02 (g) + 2 H20 (1) AH...n = -890 k] <'-’ f or 1 Mb l 414., up! -yfiokg- _ 414.7 = 1335. KT energy released = - ’3 3 5 k] 22. Draw Lewis structure of ozone (03) and indicate the electronic geometry and molecular shape at the central oxygen atom. [7 pts] - / O . electronic geometry = W :0. ‘0' molecular shape = M; 23. Ethanol (CH3CH20l-I) commonly is used as an additive to fuels such as gasoline. Combustion of ethanol occurs according to the equation given below. Determine the amount of heat (AHm) released from combustion of one mole of ethanol using the standard enthalpies of formation given below. [5 pts] CH3CH20l-I (1) + 3 02 (g) -) 2 co2 (g) + 3 H20 (1) + 02 (g) AH°I(l_<.[/mol) CH3CH20H (1) -2777 e a C02 (g) -393 .5 AHA“ = z n A”; (I’m!) - 2 A A4,: (Ma-479 3:23;!) 6285.8 =[a.(—3y3. sjr3(-ar£$+ Moj— (‘2 7Z7) * 3 (‘9) =1} 14,44. 7] ~E-a. 77. fl AI‘lrxn='_—-’3‘7 k] 24. Silver forms a crystalline metal having the cubic unit cell shown below. Each silver atom has a radius of 144 pm. Calculate the volume of the unit cell of silver in pm3. Hint: a2 + b2 = c2 (Pythagorean theorem). [5 pts] dz+ll=颥fix 341=I6r1 4": Yr" 4 = fp— =JF<I¥‘I/om) =- 5407/,“ when = .13: emf = 6.7‘1’x107/0M3 7 volume of unit cell = 6.7", X/me3 ...
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This note was uploaded on 09/01/2010 for the course BB 10294 taught by Professor Politz during the Spring '10 term at WPI.

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ch1020_2008b_finalexamsolns - MacDonald. C HM I 020, Final...

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