7#, F #\\0000<6H6H6H 6T(6|66>6x0J7N 7n9T*9~ <09T79T9TF:9T9T9T9T9T9T NAME _________________ Chemistry 142 First Exam Spring, 1995 Constants: c = 2.998 x 108 m sec-1 h = 6.626 x 10-34 J sec To = 273.2 K R = 8.314 J mol-1K-1 R = 0.08206 L atm mol-1 K-1 NA = 6.023 x 1023 mol-1 You must show all work for full credit. Please report all answers with the correct number of significant figures and units. 1) Define: State Function 2) Define: Standard State 3) Define: The First Law of Thermodynamics 4) Define: The Second Law of Thermodynamics 5) Under what condition(s) is the enthalpy change of a chemical reaction equal to the heat of the reaction (q)? 6) Fill the boxes in the following table. DH DS DG(low T) DG (high T) Spont.? - + X( ) X( ) X( ) + X( ) + + X( ) + X( ) + - X( ) - - - X( ) X( ) 7) A 65 gram block of silver metal (sp. ht. = 0.234 J/g oC) with an initial temperature of 89.5 oC is immersed in an insulated beaker of water with an initial temperature of 20.2 oC. If the final temperature of the silver and the water is 22.6 oC, what is the mass of the water? (sp. ht. water = 4.18 J/g oC). 8) Determine DHorxn for the following reaction: 5 PbO2 (s)+ 4 P (s,w) P4O10 (s)+ 5 Pb (s) element DHof (kJ/mol) PbO2 (s) -277 P4O10 (s) -2984 9) The combustion of 1.1 grams of propane, C3H8 (mwt. 44.0), with excess O2 in a perfect calorimeter produced enough heat to increase the temperature of 1000. g of water in the calorimeter by 12.2 oC. The water has a specific heat of 4.18 J/K g. C3H8 (g) + 5 O2 (g) = 3 CO2 (g) + 4 H2O(g) A) Calculate the molar heat of combustion for propane (DHrxn). continued next page 9 B) Calculate the standard enthalpy of formation for propane (DHfo) given the following standard enthalpies of formation: DHfo [CO2 (g)] = -393.5 kJ/mole; and DHfo [H2O(g)] = -241.8 kJ/mole. 10) A)Label the three regions of the phase diagram. B) Using the diagram, describe what would happen to a sample of Br2 at 1.0 atm and 25 oC if it were introduced into a large vacuum chamber.  11) Calculate the free energy change associated with the following reaction: N2(g) + O2(g) 2 NO(g) The pressure of N2 = O2 = 0.2 (atm) and the pressure of NO = 1.2 (atm). element DHof (kJ/mol) S0 (J/mol K) N2 0 191 O2 0 205 NO 90. 211 12) Find the DS for the system, surroundings, and the universe when 25.0 grams of CH4 (l) (mwt. 16.0) is evaporated at 112 K, if the heat required is provided by a room at 298 oC. (DHvap (CH4) = 9.2 kJ/mol) 13) Cu(I) is oxidized to Cu(II) by hydrogen peroxide according to the following two step mechanism. Cu+ + H2O2 Cu2+ + OH + OH- (1) {slow} Cu+ + OH Cu2+ + OH- (2) {fast} A) What is the overall reaction? B) Write the rate law for the rate limiting step. C) What is the rate of H2O2 consumption compared to Cu2+ formation? CH142:Exam I  initials _______ uvd WORD  ##! ,Times .+ P (atm) +T (K)`}ZZ"`7ZZ"E#"v# (K1.0 (}0.5""}"D +4C100 (s200 )8300 (ZPhase Diagram for Br2SecondpHcatalyst Which of the following is true about a chemical system at equilibrium? a. addition of added reactants can have no effect on concentrations b. no reactions take place c. temperature changes can have no effect on concentrations d. concentrations are stable as long as temperature and pressure are stable WriteNVH/.ABLMN[\bdefsw~R +;FG*+lm        R "*+./:;<>}~PQRS]^jkuv`abcdij % & 9 : p q 1 2 3 4 6 @ A K L M P Y ] H     V ] ( ) . / 0 3 7 8   \  PQ   @ @     Q)4ABMRSmnoWXGuv+9IJKLMOPQHI{WXþhhh$$$hh$ $$ $ $ J o p r s t ( ) L X e s t u v w H I J K L M N O P   0 1 2 d e f g ,N%pEM~d$$$hh!#@hhhP   the correct form of the equilibrium constant expression for the reaction below? Fe2+ (aq) + Sn(s) Sn2+ (aq) + Fe(s) We are studying the reaction of A + B C. If we do the reaction using [B] >> [A], then during the reaction, [B] constant, since very little of it is consumed in the reaction. We find that if we do the reaction three times, using different [B], we get linear plots of ln[A] vs. time in each case with the following slopes: [B],M slope of ln[A] vs. t, 1/s 0.10 0.35 0.20 0.70 0.30 1.05 What is the rate law for the reaction? Given the initial rate data for the reaction A + B C, determine the rate expression for the reaction. The reaction is catalyzed by molecule "D". [A],M [B],M [D],M D[C]/ Dt(initial) M/s 0.33 0.28 0.0045 1.86 x 10 -4 0.33 0.19 0.0045 1.86 x 10 -4 0.24 0.12 0.0045 9.48 x 10 -4 0.10 0.23 0.0013 4.94 x 10 -6 9)Hydrogen peroxide decays into water and oxygen in a first-order process, H2O2 (aq) H2O( ) + 1/2 O2 (g) where the rate expression is - D[H2O2]/Dt = k[H2O2]. If we begin with 0.100 M H2O2 and find that after 3200 seconds, the peroxide concentration falls to 0.0825 M, what is the rate constant, k? 10) The activation energy for 2 N2O(g) 2 N2 (g) + O2 (g) is 250 kJ. If k for this reaction is 0.380 M-1s-1 at 1001 K, what will k be at room temperature, 298 K? arean . We have the following equilibrium, PbCl2 (s) Pb2+ (aq) + 2 Cl- (aq) What will happen to [Pb2+] if: a. some solid NaCl is added to the flask? b. some solid PbCl2bbreviated 68\_vxjklmstwx e o s !!!"!#!$!&!)!+!,!Y!c!d!i!j!n!p!|!}!!!!!!!     Xd HGV^ " g o !!!!#!$!%!&!,!Q!Y!!!!!!&&&&&&&&&&&&&&&&&&&&&&&&&&''M'N'O'P'Q'R'S'T'U'V'*'*:*;*o*x*y*z*{*|*}$ $$$ $hh$$Q is added to the flask? The [H+] in an acidic soulution is 3.2 x 10-4. What is the pH and pOH of the solution? then during the reaction, [B] =O(g 8 9 10We put 2.0 g of SnI2 (fwt. = 189.5) into 100.0 mL of water. What is the iodide ion concentration in the solution? (Ksp of SnI2 is 1.0 x 10-4.) 11The concentration of Ca2+ and CrO42- in a saturated CaCrO4 solution is 0.0266 M. What is the value of Ksp for CaCrO4?12 Calculate [Cd2+] in a solutio$!!!!!!!!!!!&&&&&&&&,&?&@&K&M&N&w&&&&&&&&&&&&&&&&&'' ' ''0'2'5'6':';'H'J'M'N'U'V'X'\'l'o'q'y'z'|'''''''''''''''''''***!*'*5   @  Yn that was originally 0.01 M Cd2+ and 2.0 M NH3. K = F([(Cd(NH3)4)2+],[Cd2+][NH3]4) =1.0 x 10 7 solution 13) Calculate the equilibirum constant at 25 oC for the following reaction given DHo = -21.9 kJ/mol, and DSo = -112 J/mol T. K = F([H+][SO42-],[HSO4-]) I>MU^f     ! _ `     U V W {$ $ $ $ $*5*6*9*;*>*B*D*E*F*G*L*M*N*O*P*R*S*T*W*Y*Z*]*^*_*`*a*c*d*m*n*o*w*x*z*}***************++++++ ++++++ +!+%+&+(+)+*+.+/+0+1+2+3+4      J*}*~*************************+++3$$ $h @  $ h F@)5BCNSTbcdxyz{;~ 6>cd%RSTC Qt:IQ}Z\]^_`abcdel     ! 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