Exam 1 Answers 2002

Exam 1 Answers 2002 - Exam 1 Chem 1B(9 pts At room pressure...

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Unformatted text preview: Exam 1 Chem. 1B (9 pts) At room pressure and temperature, a balloon, on a bottle containing liquid nitrogen, was observed to expand as liquid nitrogen vaporized to produce nitrogen gas. N2 (1) —> N2 (g) Circle the correct answer for this process for each of the following quantities: q, w, and AE. q<0 (1:0 [5 E =_—.. {a + W L35 0 w > 0 W: 0 4. ~ AE<0 [AE>0! AE=0 i 41 g? {a}; g) é>g fiién. Seaiifité (9 pts) A sample of ethane gas is heated from 25°C to 75°C under conditions of constant pressure. Circle the correct answer for this process for each of the following quantities: q, w, and AB. Wiswwx : magi; L339"; q 0 W J * Pex’i’ 1? Lxfll W>0 “=0 ‘1?" AE< 0 AEzo A E : Vi (I, b T + (10 pts) Given the following data at 25°C: C (graphite) + 02 (g) ~> C02 (g) AH° = — 393.5 k] 2 H2 (g) + 02 (g) —> 2 H20 (1) AH" = — 571.6 k] 2 CZHZ (g) + 5 02 (g) —> 4 C02 (g) + 2 H20 (1) AH" = ~ 2598.8 kJ Calculate the standard heat of formation, AHf", for C2H2(g). 2 C (graphite) + H2 (g) —’ Csz (s) A H 1,; (30,, 4 QHQJ "é 3:32., i” 2376754" .. ~ n if; Q Hi i V; «wjp chay M fijl‘“ > '2‘ r 1: ~ i i L; ( C + a}: ) MW? 6” Mia “I ( ' 3' w: . 2’ L C + l _____:: v u ' :F / {/ W2 2 gecfliy ) (£453.... j/Z V,‘»—w""‘““ ““““““““““““““ ”““““*“““‘t W cm { ' g y W. :21. + H.. «7 QM? AH) 7.926.614} i i‘g méiwm b H :. J « l :. Mam/4' 6% Wu v p { J r q 1. r W; m z (2" fir’ . La? gmbi+MWx fa flu’W WWI/l £123.36” "1 ‘ dhmm jig el Efflfivfi'} 5 3W“; .1 5 :4 My! w: 2002 Exam 1 4. 5. Chem. 1B 2002 (10 pts) Consider the following reaction: 2A1(s) + 3C12(g) —+ 2A1C13(s) AH°=—1390.81kJ How many grams of A1 are required to produce 1.00 k] of heat? (12 pts) The combustion of acetylene gas, C2H2 (g), with 02 (g) produces C02 (g) and H20 (g). Given the following standard heats of formation, calculate the change in enthalpy for the combustion of 1 mole of acetylene at 298 K and 1 atm. ! HM” { by! (magi: I’XW AHf" 1k] /mol) 6 W V...” 4 C2H2 (g) +226.7 Cg H2 4 7; Cf? > 97 602 Hz ‘9 r + C7 ,_ Z L, l, H20(g) —24l.8 bli”:§Q(/'375 J/4(”Q“ll‘5) {mom/f ‘ ” W) T/wmm“ WWW”? M; 1: a Pig : "' l..(’~a l‘ 1' la Exam 1 Chem. 1B 2002 6. (6 pts) For which of the following is the process fspontaneous at all temperatures? a) AH is positive, AS is positive b) AH =0, AS is negative A H M T Ii; wax,“ V‘v’ c) AH is negative, AS is negative ““ “l” d) AH is negative, W W m e) None of these 7. One mole of liquid is vaporized at its boiling point, 800°C, and 1.00 atm. AHvap for the liquid is 30.7 kJ/mol at 80°C. a) (10 pts) Calculate w J I, K, Mg.“ CR!) \ W4 «5. l ' “f V; flywmflwwm ..... ,, I w :1 w E73 5,, 5:2 V r“ W5}, E? E A t, u, T ~r\ l 1‘ RR ; /- V » q __.i \ * k, ‘ h - l W (l)( 6'lel/ walk/l3“; ‘fl;}_w‘x//j \” “twig or 243573“ b) (10 pts) Calculate AE ‘ " r "“ ll: / I E7. ‘ weal b E. :r: “l; "t W "’l a " ’ Mr! f v a / All :2 3a,7l4"}' wzwiffii KJ 8. (12 pts) An ideal gas is compressed isothermally. d C0 W3 “l T b T; 5“ Circle the correct answer foreach of the following quantities: w, q, AH, AE, AS and AG. w<0 w=0 w :: ~ Exp bx: C‘ngVF“‘fff‘“l" WWW"; v~r~ ; “€95 :4 ‘ I L )m q>0 q=0 4' bk) w/7 51:: ’UL) AH<0 AH>0 AH=0 DH, ha,,1:f‘€”; fiawwmré W . ...... W O AE<0 AE>0 )flAgioflj DE : m CV 15:1,: 0 AS<O AS>0 As—o ‘9 “3V L: Ac; :r/éiffi «I AG < 0 AG > 0“! AG = 0 ‘ .... ,.- A G > 0: NOTE: For these kinds of problems, show the equations you need to figure out the sign of each quantity. This will help you figure out what the answer is. We will also be able to give you partial credit if you show your work. 9. Exam 1 Chem. 1B 2002 (12 pts) In a coffee cup calorimeter, 200.0 mL of 0.862 M HCl is mixed with 200.0 mL of 0.431 M Ba(OH)2. The heat capacity of the calorimeter is 453 J/°C. The initial temperature of both the HCl and Ba(OH)2 solution is 20.4800 Assume all solutions have a density of 1.00 g/mL and a specific heat capacity of 4. l 8 J 0C71 g4. For the reaction, W (m) + OH‘ (3CD —* H20 (1) the heat of neutralization is — 56.2 kJ. What is the final temperature of the mixed solution? Show your work. {460.}? {(35% ’alr‘xm :— lruz 51mg} s/ E, (3i flT’ + c: :1)? mastile C “film (“Ski ")1, ~ mail/‘63,, [fa gig/lg :«J (21515”! [jag/("j ; (7:863 M a z m (WM [5 T + Cm? i5 6! r; m 5 mew « ' w M v a to? gs 3W ‘ l k} T a (fiwgfi, Edi” _. —— , aid) ;: L if» [Igflw }{ ....... mnd>b a»? 4; ( ) !a)j(q %f§/j\lyfiaj L , 4‘ / l/ gait/(2.. for AT QNSJE, ...
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