Exam1-blank - Name BLANK Chem 230 Exam#1 Discussion Section...

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Unformatted text preview: Name: BLANK Chem 230 Exam #1 September 29, 2008 Discussion Section #: Use only the space provided to answer the questions. If you need more work space, start your answer on the back of a page and then write only your final answer in the space provided Anything written in the margins and on the back of pages will not be graded No answer that is much longer than requested will be read The use of clear diagrams or equations to answer some problems is encouraged Make sure you final answer is clearly marked The exam totals to 150 points. Multiple Choice: Mark all multiple choice clearly, by both circling the correct choice and writing the letter. Each multiple choice question is worth 3 points. 1) The hydroxide ion, OH‘, is a much stronger Lewis base than F‘. If you combined 1 mol of Co(III), 4 mols of NaOH and an excess of NaF, what would you expect the formula for the resulting Cobalt coordination compound to be, assuming it had a coordination number of 6. a) Na3[CoF6] b) Na2[Co(OH)3F3] c) Na3[Co(OH)4F2] d) Na2[CoF6] 2) Is the Co(III) free ion diamagnetic or paramagnetic? a) diamagnetic b) paramagnetic 3) If OH‘ is a strong field ligand, how many unpaired electrons would there be in the d orbitals of Co(OH)6‘3? a) 0 b) l c) 3 d) 4 4) If F‘ is a weak field ligand, how many unpaired electrons would there be in the d orbitals of COF6—3? a) 0 b) l c) 3 d) 4 Name: BLANK 5) Diamond and graphite are both elemental carbon, however diamond has a much higher lattice energy (Um). If you designed a process to convert graphite into diamond, it would most likely involve: a) an input of heat and work into the system b) a removal of heat and work from the system c) an input of heat and a removal of work d) no net change in energy 6) If the process described in question 5 is called Process A and involves going directly from solid graphite to solid diamond, then I design a second process B that involves taking graphite to gaseous carbon and then condensing it to Diamond. Would you eXpect that: a) Process A would have a greater change in overall energy b) Process B would have a greater change in overall energy c) They would both have the same change in overall energy 7) Why are the atomic 2p orbitals of F higher in energy than 0? a) Relativistic effects b) Penetration c) e' e' repulsion 8) If two transition elements join together along the z-aXis to form a metal-metal bond, which of the d-orbitals will form 6 (delta) bonds? a) dxy b) dyz C) dX2_y2 d) ClXZ e) both b and d f) both a and c 9) Vitamin B12 is an octahedral Co+3 compound. Vitamin B12 has no Relative energy levels of the d— EPR signal, which means that it has no unpaired electrons. When its orbitalsm the Square F’Vramida' methylated form undergoes enzymatic turnover, the intermediate is a geometry square pyramidal Col1 compound. Assuming the ligand field strength is the same as in the original Co+3 compound, how many unpaired electrons would there be in the Col1 intermediate? _ a) 1 b) 2 — c) 3 d) 0 Name: BLANK 10) Which of the following would have a higher heat capacity? a) H-O-H b) CEO c) N=N d) Ar 11) Which molecular orbital diagram represents a ligand that would be most likely to be involved in backbonding? 0* B) —o* C) _..*_ —..»+e 44m ——n—H—‘T—l—n—H—‘i—l—T{ as 4+0 as 12) Which of the following gases deviates most from ideal behavior? a) H2 b) CGHG C) N2 d) CH4 0* 13) Which of the following is an example of a diffusion-only process? a) The movement of perfume molecules from bottle to nose in an unsealed room. b) The movement of perfume molecules throughout a sealed container from a bottle that suddenly bursts from being heated. c) The movement of perfume molecules through a large hole from a sealed, high pressure container into a sealed vacuum chamber. d) All of the above. e) None of the above. Name: BLANK 14) You have 100 g of each of the gases below. Which gas will cause a balloon to have the largest volume at room temperature and atmospheric pressure? 21) Ne b) 02 C) N2 (1) Ar 15) A container is filled with an uncharged gas. Each time the particles collide, a photon of light is given off. Which kinetic theory assumption is being violated? 21) Pure gas is composed of many identical particles b) The particles have negligible volume c) The particles are moving randomly d) The gas particles only interact with each other during collisions e) All collisions are elastic 1) None of the above 16) Which type of solid is held together primarily by electrostatic forces? a) Metallic b) Covalent c) Molecular d) Ionic e) All of the above 1) None of the above Short Answer Answer these questions using a maximum of two sentences per part. Often a word or phrase is enough. The space provided is an indication of the number of words necessary. Where requested you need to show a diagram or work to receive full credit. 17) ( 6 pts) Why would you eXpect to be the Sc 3d orbital to be higher in energy than the Ti 3d orbital? Name: BLANK 18) ( 6 pts) What 3 conditions must be true for a gas to exhibit the the Maxwell-Boltzmann distribution? a) b) c) 19) (12 pts) Given the enthalpies of formation below, calculate the enthalpy of the following reaction (for this problem, include your final work within the space provided): 2C2H6+702—>4C02+6H20 Enthalpies of Formation 2 C(graphite) + 3 H2 —> C2H6 A “f: -100 1/2 02 + H2 —> H20 AHOF C(graphite) + 02 —> C02 AH°F -400 6 C(graphite) + 3 H2 —> CGHG A “f: 100 20) (10 pts) A molecular orbital diagram of a fifth row transition element metal-metal bond would look exactly the same as a diagram for the third row transition elements except that the contributing orbitals would be the 6s and the 5d orbitals. Draw a molecular orbital diagram of the d-orbitals and s-orbitals forming the molecular orbitals in a metal — metal bond. Using the diagram, calculate the bond order of W2. Name: BLANK 21) (8 pts) What is the difference between Lattice Energy (U) and Lattice Enthalpy (H)? 22) (17 pts) Draw the relative energy levels in the d-orbitals for splitting by Crystal Field Theory that would occur in a trigonal planar compound, this is a three coordinate compound with all ligands in the XY plane, with one lying on the X-aXis and two in between the X-Y aXis (see diagram). 23) (8 pts) In an octahedral Ru+2 compound, give the number of unpaired electrons in a high-spin state and a low-spin state? Calculate the same comparison for: Ru”, Rh”, Rh”. Show your final answer in the form of a table. Name: BLANK 24) (5 pts) You have two containers of ideal gas as shown below. For each scenario, rank the boxes in terms of the indicated property (i.e., He < Ar, He = Ar, or He > Ar). 4— L —p- He (4 gimol) Ar (40 gr’mol] a) The two containers have the same temperature. Rank the gas particle velocities. b) The two containers have the same temperature and pressure. Rank the number of moles. c) The two containers have the same temperature and density. Rank the pressures. d) The two containers have the same temperature and pressure. Rank the collision frequencies. e) The temperature of the Ar box is 10 times higher than the temperature of the He box. Rank the volume occupied by the individual gas particles, assuming non-ideal behavior. 25) ( 6 pts) Henry's Law is P : kx, where P is the partial pressure of the gas and x is the mole fraction (concentration) of the gas in solution. The constant k is about l3xlO‘4 for 02, 6.5x10‘4 for N2, and 14x10‘4 for Ar. Given that the atmosphere is approximately 21% 02, 78% N2, and 1% Ar, explain which gas has the highest dissolved concentration in a glass of water, and why. Name: BLANK 26) (12 pls) A rigid vessel contains a high pressure of hydrogen and nitrogen. When heated in the presence of a metal catalyst, the two react to form ammonia according to: 3 H2+2N2->4NH3 a) Immediately following the reaction, is the pressure higher, lower, or the same as before the reaction, assuming the reaction itself does not alter the vessel temperature? b) If the container explodes due to the high internal pressure immediately following the reaction, what can you conclude about whether the reaction produces heat? c) NH3 does not behave as an ideal gas in the vessel. Give two reasons why not, and which term (if any) of the van der Waals equation corrects for each. 27) (12 pls) 100 g of a gas is predicted to have a pressure of 1 atm in a rigid container at room temperature using the ideal gas law. a) If the measured pressure in the container is lower than 1 atm, which parameter (if any) of the van der Waals equation is dominant for this gas? Briefly justify your answer. b) If the measured pressure in the container is greater than 1 atm, which parameter (if any) of the van der Waals equation is dominant for this gas? Briefly justify your answer. c) If the pressure is 1 atm at room temperature, is the pressure likely to be higher, lower, or the same as the ideal prediction when you heat the vessel to several thousand degrees? Briefly justify your answer. ...
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