Chemistry 271 Section 22xx Your Name Prof Jason Kahn University of Maryland College Park Your SID General Chemistry and Energetics YOUI Section or time Final Exam 200 paints total Decemb er 16 2011 VIEWING Monday May 19 9 30 10 30 a m Chem 1356 1360 YOLI have 120 minutes for this exam Explanations should be concise and clear There is ex tra space on the last page if YO LI need it You will need a calculator for this exam No other study aids or material s are permitted Ge nerous partial credit will be given i e if YOLI don t know guess Useful Equations K W A HA pH log W Kw W HO pH pK log A l HA R 0 08206 L atlnlmole K S qlT 0 S k81n W W N CTI n k8 1 38 X 10 23 J K R 8 3 14 J m o le K b Go RTlnKeq InKeq tJJr I RT SoIR 1 987 cal mole K N AkB b G N T M E L n i Ci n lno ex p Ei EO lkT N L ni Chemical s tandard state 1 M solutes p ure liquids 1 atm gases Biochemical s tandard state pH 7 all species in the ionic form found at pH 7 C OK 273 15 P v dv Cv 2exp rnv 2 2kT E EO 2 303 RTln J logIOQ 2 303RTlc F 0 0592 Volts at 25 C 60 nc FEo cell A A o kt Standard hydrogen electrode c F 96500 C o Lil omb mole In k E IRT In A In A In AJ o kt 2 W aq 1 M 2 e 7 1 Volt 1 JOLile Coul omb 1 AJ l AJ o 2kt H g EO 0 000 V Honor Pledge At the end of the examination time please write out the following sentence and sign it or talk to me about it I pledge on my honor that I have not given or received any unauthorized assistan ce on thi s examinatioll 2 pts Chemistry 271 Final Exam 1211612011 1 21 II 24 pts Multiple choice Circle the single best answer for each question a 4 pts If the rate law for a process A B I the 2 the 0the 4 the t C is observed to be Rate k A B reaction must be an elementary reaction reaction cannot be an elementary reaction reaction might be an elementary reaction expe riment was done wroug b 4 pts If the rate law for a process A B t C D is observed to be Rate k A 2j C 1 the reaction must be an eleme ntary reaction he reaction cannot be an elementary reaction 3 the reaction might be an elementary reaction 4 the experiment was done wrong c 4 pts The melting temperature in DNA hybridization I increases with the number of mismatches between target and probe increases with the len gth of the complementary region 3 increases as the concentration of DNA decreases 4 None of the above el 4 pts Cyclic reactions A t B t C t A I are imposs ible can proceed in a net forward direction as drawn only if we heat the reactio n to drive it Q Iat equilibrium must also proceed in reverse at the same rate for each step 4 None of the above 5kl e s Nitrogen fixation describes conversion of N2to NH 3 2 NH to NOJ 3 N03 to N2 4 NH3 to N0 3 CJ f5 f 4 pts The lead acid battery used in cars is so large and heavy because I the weight of the battery is needed to adjust the car s suspension 2 it needs to store a lot of energy to recharge the alternator while driving it needs to have 60 internal cells to provide 120 V to the distributor and the car s electronics t1 the starter mo tor requires high power and therefore current to move the pistons in the engine 9 Score for the page I 2 L L Chemi slrv 271 2 in 1 Exam 121 12 11 311 48 pts Kinetics Rate Laws and Arrhenius N2 g O2 g 2NO g The rate consta nt k for this reaction which occurs during combustion as a precurso r to NO in s mog formation is 3 18 u nits at 2000 K and 7396 units at 2400 K Derived from G il bert 15 85 a 6 pts Write down the rate law for the reaction assuming that it is elementary What are the units for the rate constant rG t cl l c Co J IV i 1 J deNO Nryl OLl dt 3 1 il P 2Poz t Q j oM T hil three l M b 12 pts Ca lcul ate the activatio n energy Ea and the pre exponential factor A for the reaction E IZ 31 is JV I Po e NI S I to j ZT e r n I 3 OOC ice 4 Zax Ae I 2 t e I A z fot w G t yf 5 e Ie D i 10 tvI s I c 6 pts Calcu late the rate constant at 300 K Given that NO is poi sono us it s a good thin g the reaction is slow at anythin g cl ose to room temperature 5 04 iO i IDe 140 DO S I l 1 3CDI rt 1 Score for the page J t JY el l o0 Chemi stry 271 Final Exam 1211612011 10 d 12 pts The half life of m Cs one of the main radioactive pollutants from the Fukushima and Chemobyl disasters is 30 2 years From the integrated rate equation for a first order reaction derive an expressioll for the half I ife in terms of the rate constant and calculate the rate co nsta nt for Cs 137 decay CAl 14 0 o t t VI J do 1 h e b O b9 1 CAlo A J r 1 2 01 e i t j Q i l l i I In I In J k e 12 pts Explain the functional form of the Maxwell Boltzmann di stribution P v dv In other words where do the y Cy exp mv 12kT 2 and exp my 2kT factors come from Explain why doubling the temperature typically causes much Jl ore than a factor of 2 increase in the rate of elementary processes c ome fY f i ht VQ c i 1 e 1 Y1 1 2 r S d roc tht i W 1 d he o V H h e E i lfrT MQ V i l C 3f ere ts h e i rG d s 1 0 lhmo I Y R ve J rc i or 0 blA tiow1 ihcd m iv ivyv z eg h c 00 i rrti cle Mn t ctte5 pouolih 1 yW6 ft c 1v e Q iQ Jje 9 lV d stD b 4 G Yl tt t 0 fCAC tor i J I …