7#$ K3q(\\0000X888 8(8889x0f.9x 9:q*:_0:q9:q:qJ9:q:q:q:q:q:q NAME _________________ Chemistry 142 Third 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 Kw = 1.0 x 10-14 M2 F = 96,400 C/mole You must show all work for full credit. Please report all answers with the correct number of significant figures and units. 1) Define: oxidizing agent 2) Define: buffer capacity 3) The following reactants are mixed in equal molar portions. Predict if the resulting solution will be acidic, basic, neutral, or if there is not enough information given to tell for sure. HCl(aq) + Ca(OH)2 (aq) --> ? 4) Given the two following half reactions, Ni2+ (aq) + 2e - Ni(s) Eo = -0.25 V Hg2+ (aq) + 2e - Hg(l) Eo = +0.86 V calculate Eocell for the following reaction: Hg2+ (aq) + Ni(s) Ni2+ (aq) + Hg(l) 5) Consider the following half reactions: Cl2 (aq) + 2e - 2 Cl- (aq) Eo = +1.36 V Sn2+ (aq) + 2e- Sn(s) Eo = -0.137 V Al3+ (aq) + 3e - Al(s) Eo = -1.66 V (a) Which species wants to be oxidized the most? ___________________ (b) Which species will reduce Cl2? ______________________________ 6) We have 100. mL of a 0.10 M solution of CH3COOH. How many grams of NaCH3COO (fwt. 83. g/mol ) must be added to make a buffer solution of pH = 5.00? Ka (CH3COOH) = 1.8 x 10 -5 M. 7) The Ka for the dissociation of hypoiodous acid (HIO) is 2.00 x 10-11 M. What is the pKb for its conjugate base? 8) We have 500. mL of a 0.10 M NH3 solution. We add 1.0 mL of 10.0 M HCl. What is the pH of the resulting solution? pKb (NH3) = 4.75 9) We have 200. mL of 0.10 M HClO solution. pKa (HClO) = 7.46 a) What is the pH of the resulting solution after 50 mL of 0.40 M NaOH is added? b) What is the pH of the resulting solution if only 25 mL of 0.40 M NaOH is added? 10) Consider an electrochemical cell where the following reaction takes place: 2 Au3+ (aq) + 3 Zn(s) 2 Au(s) + 3 Zn2+ (aq) Draw the cell labeling the parts (anode, cathode, etc.). Indicate which direction electrons will flow in the cell. 11) Eo for the following redox reaction is +1.05 V. 2 Ag+ (aq) + Ni(s) 2 Ag(s) + Ni2+ (aq) What is DGo and K for this reaction? 12) Determine the cell potential for Cu(s) + Pt2+ (aq) Cu2+ (aq) + Pt(s) where [Cu2+] = 0.85 M and [Pt2+] = 0.0070 M using the following standard reduction potentials. Pt 2+ (aq) + 2e - Pt(s) Eo = +1.20 V Cu2+ (aq) + 2e - Cu(s) Eo = +0.34 V CH142:Exam III  initials _______ uvFinal Short Answer and provide two examples of a Hard Lewis Acidpolydentate ligandDefine: The Third Law of ThermodynamicsWhat is the pH of a solution prepared by adding 1x10-8 moles of HCl to a liter of pure water.? (Think before you write!) Which species is being oxidized in each of the following reactions? a) 4 NH3 + 5 O2KLMZ[acderv}~w  &(67PQvw{ &'@AUWcd{|@      V@Ad+-DE=>BC   k m t u x z    5 6 Q S b c { |    . V b d @ @   V)4ALxrz]eMdlm13456789:;<MNOPQRST$$$$ $hh$ $$ $ $ OTUVWXYZ T U V W X Y Z [ \ ] ^ H y z { | } ~  $ % & ' ( ) * + , - . S [  A I  $ $hh!#@$$$$R   = 4 NO + 6 H2O b) H2O2 + Cl2 + 2 OH- = 2H2O + 2 Cl- 6) 5) Write the net ionic equation for the complete neutralization of H2SO4 (aq) with NH3 (aq). Long Answer7. When 182 grams of gold is added to 22.1 grams of water at a temperature of 25.0 C the final temperature of the resulting mixture is 27.5 C. If the heat capacity of gold is 0.129 J/g K, what was the initial temperature of the gold sample? (heat capacity of water is 4.18J/gK) 8) The standard molar enthalpy change is -905.2 kJ for the oxidation of ammonia: 4 NH3 (g) + 5O2 (g) = 4 NO(g) + 6 H2O(g) Calculate the standard molar enthalpy of formation for ammonia based on the following standard enthalpies of formation: DHf [NO(g)] = +90.3 kJ/mole; and DHf [H2O(g)] = -241.8 kJ/mole. 9) We have 20.10 M sodium hypobromite0.0 mL of 1 aHBrO8.7010) We have 16ammoniabNH34.75ting solution after 40 mL of 0.2HNO3 bting solution after 80 mL of 0.2HNO311 Calculate [Cd2+] in a solution that was originally 0.01 M Cd2+ and 2.0 M NH3. K = F([(Cd(NH3)4)2+],[Cd2+][NH3]4) =1.0 x 107 12The rate constant for the second order reaction 2NOBr(g) 2NO(g) + Br2(g) is 0.80 M-1s-1 at 10oC. Starting with a concentration of 0.086 M of NoBr, calculate its concentration after 22 seconds. 13) Given the same initial concentrations, the reaction CO(g) + Cl2(g) COCl2(g) at 250 oC is 1.50 x 103 times as fast as the same reaction at 150 oC. Calculate the energy of activation for this reaction. 14A 200. ml solution of 0.400 M HCl is mixed with 200. ml of 0.200 M Ba(OH)2 in a constant pressure calorimeter having a total heat capacity of 453 J/oC. The initial temperature of both solutions is 20.5 oC. Given the heat of neutralization for the process H+ + OH- H2O is -56.2 kJ/mole, what is the final temperature of the mixed solution? 15) The space shuttle uses fuel cells for electricity, and one cell that has been proposed is based on hydrazine, N2H4 , and O2 . The reactions are a. N2H4 (aq) + 4 OH- (aq) N2 (g) + 4 H2O(l) + 4e- b. O2 (g) + 2 H2O(l) + 4 e- 4OH- (aq) (i) Which reaction occurs at the anode? ____________ (ii) If the cell is to produce 0.50 amps of current for 25.0 hours, how many grams of hydrazine (N2H4) must be present? (1 Faraday = 96,500 coulombs/mol e - ) and provide two examples of a H o /a concentration of 0.086 M of NO 16) When 0.050 mol of propionic acid (C2H5COOH) is dissolved in 500. ml of water, the equilibrium concentration of H+ ions is 1.15 x 10-3 M. What is the Ka for this acid. 17) One of the possible sources of acid rain is the reaction between nitrogen dioxide, a pollutant from automobile exhausts, and water: 2NO2(g) + H2O(l) 2 HNO3(g) + NO579:<?PR d l \ijklqrstyz  +0:;<=EFGHJ%Kghijv @\ !%9;EGHIK_`akmnoq89EFTVWY_`  #$-./023^_f    Y23ijyz{|  / 0 P Q R S T t u w x y z !!!!!&!+!-!!!!!!!!!  ] lmC19;=>?@ABCDEFGH,v,-JK$$ $=$ $hh$ $$$$$LI#+iq / 0 Q u v w x y!'!(!)!*!+!,!-!.!/!0!1!2!3!4!!,,,,,,,--9-Z$$$$$-(g) Determine whether this it thermodynamically feasible (A) under standard conditions and (B) at 298 K, with each gas present at p= 1.00 x10-6 atm. Species DHo kJ/mol DSoJ/mol K DGo kJ/mol NO2 (g) 33.18 240.6 51.31 H2O (l) -285.8 69.91 -237.1 HNO3 (g) -135.06 266.38 -74.72 NO (g) 90.25 210.76 86.55 -9 + OH-NaBrOHBrO.spontaneous:, Final Exam @HTUVWXYZ[\GH!,,%,;,=,>,^,w,x,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,--- ------ -#-*-+-1-2-8-9-;-@-A-F-K-W-Y-Z-[-f   @M@ (Z B `X@)4ALwx  $%&'(&n.6hp?GSTUVWXYZ[:;TU ` a b c d e f g h i = > ? @ A B C I J \ ] < P X   i  !HI4U$$$$$$$$$$$$$$$$$$$$$$$$ $ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$ $$$$$$$$$$$ $$$$$$$$$$$ $!$$%$$$$$$$$$$$$$$$ $ $$$$$$$$$$$$$ $ $$$$$$ $A$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$'*@ d!-fT -Z   &p&r9HH(EG(HH(d'@=/RBH-:LaserWriter 8 ChicagoNew YorkGenevaMonaco Zapf DingbatsPalatinoTimes HelveticaCourierSymbol DeltaSymbol&p Espy Sans&rEspy Sans Bold9 eWorld TightERRQJOJOMH).wx :FHPq "#$&+noprs~Db-6@AJKQTbc !"&'JVYZ[\ht{*+-048Znpz~AG  . _ d g i k   * < = A C E G   M N S U V W X Y Z [ ] _  STfhz{%&-.45;<Dcoqst%&,-378<EFMNTWX[bcijpqwx .̀   ƀx 0      . V-9 d l  ̀   ɀ    \ijklqrstyz-;-@܀݀ހ Pln Q^̀   R+ S-0:;<=EFGHJ^€ŀӀԀ%Kghijvǀʀˀ̀̀ʀـ-A-F>CK h|!%9;ۀEGHIK_`aۀkmn To `q y 89EFTVWY_` T #À (ƀȀ   *#$-./023^_f + , 023ij t u w x y z      !!!!!&!+!-!!!!!!!!,-K,9,;,=,>-W,W,^,w,x,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,--- ------ -#-*-+-1-2-Y -Z-[    9Final-Spring-1995College Use OnlyCollege Use Only