GEN CHEMISTRY II
GEN CHEMISTRY II CHM 1046
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This 27 page Class Notes was uploaded by Ubaldo Dach on Thursday September 17, 2015. The Class Notes belongs to CHM 1046 at Florida State University taught by Staff in Fall. Since its upload, it has received 59 views. For similar materials see /class/205694/chm-1046-florida-state-university in Chemistry at Florida State University.
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Date Created: 09/17/15
Name Section Number TA IF YOU DON T HAVE YOUR CORRECT SECTION NUMBER THIS ASSIGNMENT WILL NOT BE GRADED This 39 should be mhmittpd to 208HTL 0n Mondav 13quot 2010 at 1200 PM NO LATE SUBMISSIONS ARE ACCEPTED Bonus assignmentZ 11046 Fall 2010 3 points worth 1 Which of the following substances has London dispersion forces as its only intermolecular force A CH3OH B CH4 C HZS D NH3 E HCl 2 Which one of the following exhibits dipoledipole attraction between molecules A AsH3 B C12 C BCl3 D C02 E XeF4 3 The predominant intermolecular force in CH32NH is 7 i A London dispersion forces B ionic bonding C hydrogen bonding D iondipole forces E dipoledipole forces 4 Which statements about viscosity are true i Viscosity increases as temperature decreases ii Viscosity increases as molecular weight increasesi iii Viscosity increases as intermolecular forces increase A i only B i and iii C ii and iii D none E all 5 The shape of a liquid39s meniscus is determined by if A the type of material the container is made of B the relative magnitudes of cohesive forces in the liquid and adhesive forces between the liquid and its container C the amount of hydrogen bonding in the liquid D the viscosity of the liquid E the volume of the liquid a The Vapor pressure of a hqmd decteases lmearly wnh Increasing temperature In E E 539 1 a E e 3 5 v E decteases nonlmearly thh mueasmgtempemture 7 Canal tm v n tt t tt mnvmy above 279 C 82 can only occur as a A hqmd B solid C hqmd and gas D supexmucal md E gas 8 Heat of subhmation can be approximated by addmg together and A heat of deposmon heat ofvaponzauon B heat of heeztng sahdmcatmn heat of condensation C heat of fusmn heat aponz D heat of freezmg sohdmcauon heat of Vaponzauon E heat of fusion heat of condensauon D z Exandy 0 10 0 10 20 30 40 50 60 70 T C 10 39 39 39 39 r 39 above is cl A 10 B 20 C 30 D 40 E 50 11 The phase diagram ofa substance is given above This substance is a at 25 C and lo Imnl A supercritical uid B crvstal D gas E liquid 12 On a phase diagram the critical pressure is A the pressure above which a substance is a liquid at all temperatures B the pressure at which a liquid changes to a gas 39 liquefy a a 39 E the pressure required to melt a solid 13 On a phase diagam the critical temperature is 777 A the temperature below which a gas cannot be liquefied B the temperature required to cause sublimation of a solid C the temperature required to melt a solid D the temperature above which a gas cannot be liquefied E the temperature at which all three states are in equilibrium l4 TRUEFALSE a The boiling points of normal hydrocarbons are higher than those of branched hydrocarbons of similar molecular weight because the Londondispersion forces between normal hydrocarbons are greater than those between branched hydrocarbonsii b Heats of vaporization are geater than heats of fusion i c The value of the boilingpointelevation constant Kb depends on the identity of the solvent d The overall reaction order is the sum of the orders of each reactant in the rate law 7777 15 Which of the following molecules are polar 16 De ne each type of intermolecular force below Give an example of each and describe what characteristic that example has that results in each type of intermolecular force A Ion dipole B Dipole dipole C London dispersion forces D Hydrogen bonding 17 List ALL the intermolecular forces that exist between molecules in each of the following Circle the strongest force that will determine physical propem39es eg boiling points for each substance CH3C1 H7 Ne NH 3 HF CH3OH C2H4 CO 18 Complete the following table 19 Explain the intermolecular forces that compete to determine Whether or not an ionic substance will dissolve in water Which force must be strongest in order for an ionic substance to dissolve 20 How are boiling points affected by intermolecular forces 21 Define surface tension and Viscosity How do intermolecular forces affect these properties ie as intermolecular forces increase what happens to each property 7 22 List the 6 types of phase changes Solid 9 liquid Reverse Liquid 9 gas Reverse Solid 9 gas Reverse 23 List and explain the following substances in order of increasing boiling points BaC12q H2 CO HF Ne C02 24 Heats of vaporization are always larger than heats of fusion why 25 What is meant by normal boiling point and normal melting point 26 a Draw the phase diagram for water Label each section and the phase changes that occur at each line Identify the normal boiling point and normal freezing point for water b What happens to the melting and boiling points of water as pressure is decreased 27 Identify the main intermolecular force in the following compounds You may find it useful to draw Lewis structures to find your answer a PF3 b H2CO c HF 28 Explain how dipole dipole forces cause molecules to be attracted to one another 29 Rank the following compounds from lowest to highest boiling point calcium carbonategq methane methanol CH4O dimethyl ether CH30CH3 30 Explain why nonpolar molecules usually have much lower surface tension than polar ones 31 Liquid ammonia boiling point 334 C can be used as a refrigerant and heat transfer uid How much energy is needed to heat 250 g of NH3l from 650 C to 120 C Specific heat capacity N H3l 47 JgoK Specific heat capacity NH3g 22 JgoK Heat of vaporization 235 kJmol 32 The ourocarbon compound C2C13F3 has a normal boiling point of 476 C The specific heats of C2C13F31 and C2C13F3g are 091 Jg K and 067 Jg K respectively The heat of vaporization for the compound is 2749 kJmol Calculate the heat required to convert 25g of C2C13F3 from a liquid at 500 C to a gas at 8200 C 33 How many kilograms of CC12F2 must be evaporated to freeze a tray of water at 0 C The mass of the water is 525 g the heat of fusion of ice is 601 kJmol and the heat of vaporization of CC12F2 is 174 kJmol 34 The vapor pressure of ethanol is 115 torr at 349 C If AHWP of ethanol is 405 kjmol calculate the temperature in 0C When the vapor pressure is 760 torr 35 Calculate the total energy needed to change 20 grams of ice at 1 0C to water vapor at 120 oC MP 0 0C BP100 oC The specific heat of water 4186 joulegam C The specific heat of ice 209 joulegam C The specific heat of water vapor 201 joulegam C AHCmdensmon of water 4067 kJmol AHquon of water 602 kJkg 2 hints which I won t mention in the exam 1 watch the units in AH 2 Check if you have the correct AH Do you need AHfusion or AHmemng AHWWWon or AHwndenmon Use the correct AH you may need to look to slide number 26 in your notes 36 Calculate the final temperature of 17 grams of water initially at 10 C if 5 k of energy is added to the system in the form of heat The specific heat of water 4186 joulegam C The specific heat of ice 209 joulegam C The specific heat of water vapor 201 joulegam C AHCmdenmion of water 4067 kJmol AHfusion of water 602 kJkg you may not need all the above information to solve this question 37 Calculate the final temperature of 17 grams of liquid water initially it was ice at 10 0C if 10 k of energy is added to the system in the form of heat initial state is solid amp nal state is liquid The specific heat of water 4186 joulegam C The specific heat of ice 209 joulegam C The specific heat of water vapor 201 joulegam C AHCmdenmion of water 4067 kJmol AHfusion of water 602 kJkg you may not need all the above information to solve this question 38 Dichloromethane CHzClz 2 chlorines is an organic solvent used for removing caffeine from coffee beans The following table gives the vapor pressure of dichloromethane at various temperatures HINT watch the units V E a Find the value in kJmole for AHvap using the Clausius Clapeyron equation for two data points pick any two data points b Find the value in kJmole for AHvap for dichlormethane using the plots or the equation of the line from the Clausius Clapeyron equation plot plot should be drawn by hand you are not allowed to use excel c How does the two values in a and b compare to each other which is more precise e What would be the vapor pressure at 250 C f Calculate the normal boiling point in OC Practice Problems Chemical Kinetics 1 For the reaction given below what is the rate for each of the reactants and products 3A2Bgt4C 1AA 1AB 1AC 3 At 2 At 4 At 2 Given the following experimental data nd the rate law and the rate constant for the reaction N0 N02 g 02 g quot N205 g Run NO0M N020M 02M InitialRateMs391 1 010M 010M 010M 21X10392 2 020 M 010 M 010 M 42 X 10392 3 020 M 030 M 020 M 126 X 10391 4 010 M 010 M 020 M 21 X 10392 2 Rate kNO N02 k 21 M ls 1 3 The halflife of a radioisotope is found to be 455 minutes If the decay follows rst order kinetics what percentage of isotope will remain after 200 hours k0152 min39l AL 115x103960o notmuch 4 The mechanism of a reaction is shown below HOOH 1 gt HOI 0H7 slow H01 1 gt 12 0H7 fast 20H 2H30 gt 4H20 fast a What is the overall reaction b Which compounds are intermediates c Predict the rate law based on this mechanism d What is the overall order of the reaction 4 a Overall reaction HOOH 217 2H3O gt 12 4HZO b Intennediates 0H7 and HOI c Predicted mechanism Rate k HOOH17 d Overall order 2quotd order 5 For the reaction A B gt C the rate constant at 215 0C is 50 X 10393 and the rate constant at 452 C is 12 x 101 a What is the activation energy in kJmol b What is the rate constant at 1000 C 5 a 394 kJmol b 250 x 10394 s391 6 Balance the equation below and determine the rate expression using the given data Find k with units N2 H gt NH3 all gaseous Rate balanced equation N2 3 Hz 0 2 NH Rate Law Rate 1ltN2aH2b Find b 0008400021 020010b 4 2 so b 2 Find a 0067200084 020010a0400202 82342 23 soa1 Rate Law Rate 1ltN2H22 Find k with units 00021 Mmin 1lt010M010M2 k 00021 Mmin00010 M3 k 21 1M2min 7 The decomposition ofNOCl to NO and C12 has k 93X10395 1Ms at 100 C and k 1010393 1Ms at 130 C What is the activation energy ofthis reaction Use the combined Arrhenius equation 111k2k1 EAR1T1 1T2 k1 9310395 lMs when T1100C or 373K k2 1010393 1Ms when T2 130C or 403K ln10x1039393X10395EA83l45 JmolK1373K 1403K 375 EA240x1039f EA 2375240X10quot 99000 Jmol or 99 kJmol 8 The halogen astatine can only be obtained arti cially through bombardment It has been found to be useful for the treatment of certain types of cancer of the thyroid gland One form of radioactive astatine is an a particle emitter with a halflife of 721 hr If a sample containing 0100 mg of astatine is given to a person at 9 am one morning how much astatine Will remain after about 14 hours Halflives are constant for rst order reactions 1112 kthalf thalf 721 hr so k ln2721 hr 00961 hr391 ln nalinitial kt ln nal0100 mg 00961 hr39l14 hr 135 fmal0100 mg eA135 0260 nal 02600 100 mg 0026 mg astatine remaining 9 It took 143 seconds for 500 of a substance to decompose Ifthe initial concentration was 0060 M and the reaction is rst order what is the value of the rate constant with units thalf 143 seconds so k ln2143 s 000485 s391 10 In the following decomposition reaction 2 N205 gt 4 N02 02 oxygen gas is produced at the average rate of 91 X 10394 mol L391 s39l Over the same period what is the average rate of the following the production of nitrogen dioxide the loss of nitrogen pentoxide From the equation we see that for every 1 mole of oxygen formed four moles of nitrogen dioxide are produced Thus the rate of production of nitrogen dioxide is four times that of oxygen rate N02 production 4 X 91 X 10394 mol L39l s39l 36 x 10 3m01 Lquot s 1 Nitrogen pentoXide is consumed at twice the rate that oxygen is produced rate loss ofN205 2X 91 X 10394 mol L39l s39l 18 x 10 3 mol L391s391 11 If the rate of loss of hydrogen gas is 003 mol L39l s39l what is the rate of production of ammonia Consider the following reaction N2 3 Hz gt 2 NH3g S olution From the balanced equation we see that there are 2 moles NH3 produced for every 3 moles Hz used Thus 2 rate NH3 production X 003 mol L39l s39l 3 002 mol L391 5391 12 Consider the reaction below 2 Hzg 2 we a 2 H20g N2g Initial rate data for this system are given below Determine the rate law and the value of k the rate constant show units Initial concentration Initial rate H2 No mm Hg mirv 1 6 30 2 6 4D 3 6 I50 18 1 10 18 2 4O 13 3 9D 2 3 rate kH2NO k 056 mm HgM min 13 For a certain reaction the following data were obtained temperature 0C 20 40 50 60 ks1 25 x 10395 27 x 10394 91 x 10394 29 x103 By graphical means graph paper attached determine the value of the activation energy Ea for this reaction Determination of EE y 11554x 23788 500 500 100 E 000 900 39mm 39 much In R 1100 000341 1050 000290 000310 000330 000350 000319 322 1 000310 00 quotT m 3 000300 534 slope 11554 EaR 4 therefore Ea 96 X 10 Jmol 14 Consider the following reaction N02 CO gt NO C02 A suggested mechanism is given below N02 N02 gt N03 NO N03 CO gt N02 C02 If the rate law is known to be kN022 which of the two steps is slower Which substance if any is probably an unstable intermediate The rst step would be slow since all of the ingredients for the rate law are found in the reactants of that step N03 which is produced in one step consumed subsequently and does not appear in the net reaction is an intermediate 16 The initial rate of the reaction Broaaq 5 Br aq 8 Haq gt 3 BI 21 H200 Has been measured at the reactant concentrations shown in molL Experiment Br03 Br Hl Initial rate molLs 1 0 0 010 0 0 80 x 10 4 2 020 010 010 16 x 10393 3 010 020 010 16 x 10393 4 010 010 020 32 x 10393 According to these results what would be the initial rate in molLs if all three concentrations are Br0339Br39H020 mollL 17 Using the kinetics data below rst determine the orders for AB and C Once the orders are correct determine the value of the rate constant A B C RateMsec Trial 1 15 030 050 43quot 10393 Trial 2 050 010 050 16quot 10394 Trial 3 15 010 050 4710394 Trial 4 15 030 10 85quot 10393 The Rate Law Obtaining reaction orders for simple processes where the data is well designed can usually be done by examination The presentation here will follow that approach For the reaction data shown here the orders are determined as follows The order in A is obtained by comparing Trials 2 and 3 It can be seen that the concentration of A was tripled while the reaction rate triples as well indicative of a rst order process The order in B is obtained by comparing Trials 3 and 1 It can be seen that the concentration of B was tripled while the reaction rate increases ninefold The rate law would be second order The order in C is obtained by comparing Trials 1 and 4 It can be seen that the concentration of C was doubled while the reaction rate doubles also indicating a rst order rate process The Rate Constant Once the rate law is obtained the rate constant can be evaluated by making the appropriate substitutions into the rearranged general rate equation Using the data from Trial 1 yields kRateAaBbCc 4310393151030205016310392 M393sec391 18 Use the kinetic data provided below for the hypothetical reaction A B gt C D 1 To determine the order of the reaction with respect to A 2 To determine the order of the reaction with respect to B 3 To write the rate expression or rate law for the reaction 4 To calculate the rate constant of the reaction Starting With Rate k Ax By 1 To determine x the data from experiments 46 are used because A varies While B remains constant in these experiments A plot of log rate vs log A for experiments 46 gives a slope of about 2 Figure l The uncertainties in the concentrations and rates are around 2 Therefore x 2 Within experimental uncertainty Figure 1 log rate vs log A O 112 E g 04 y 20456x 07336 g R 99994 416 08 I 0 8 0 6 04 0 2 log A 2 The value of y can be determined by plotting log rate vs log B for experiments 13 This yields a slope of about 1 Figure 2 Therefore y 1 within experimental uncertainty Figure 2 log rate vs log B 5 14 g l I a I y 09982x 09944 2 48 quot R309997 2 22 I I I I I 12 39 08 06 04 412 0 3909 31 3 Rate k A2 B 4 The rate constant k can be determined from data in any one experiment For example using the data in experiment 3 00403 Msec k 0100 M2 0400 M or k 101 M2sec1 19 The reaction 2 NOg 2 Hzg gt Nzg 2 HzOg is found experimentally to be second order in NOg and rstorder in Hzg a Write the rate law for the reaction b What is the overall order of the reaction c What are the units for the rate constant k d If NO is doubled while keeping Hz constant by what factor will the reaction rate increase e If Hz is doubled While keeping NO constant by What factor will the reaction rate increase Answers a rate V k NO2 Hz b third order overall c L2 mol392 s39l d 4fold e rate will double 20 Label reaction coordinate gt Solve the following problems from your book Number 32 Number 47 number 60 number 89 and number 92 hint for part a in N there are triple bonds
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