05/15/14 CHEM 1A Final Exam k!z7 Answ.(?S" Name: Please read the following. To receive full credit for a question or a problem, in addition to the correct answer, you must show a neat, complete, and logical method of solution where each number is labeled with the appropriate unit and the final answer is rounded to the correct number of significant digits. The correct answer without any work shown will generally get zero credit! When an explanation is required, it should be brief, but accurate and complete. There are 16 questions for a total of 200 points. 1. (IJS"points) A 10-L container at 0°C is filled with 0.200 moles of oxffe'n, 0.500 moles C () carbon dioxide, and 0.300 moles of methane. C llt.j 'f) (a) How many substances are present in the container? -1h ree ; (}'fi:r u_ ( 0} J ca.s: boru:it'oy/de- ( cu01 ) (b) How many elements are present in the container? 1 aud ~ -!fuz_t...e__ ( Cffy) (Nfcf11 ( O) 1 cc:sbon (C), ~~ hyc!'i?11 (II) -lhree : (c) How many molecules are present in the container? o, duO ~1 od o, + soo~! c:.Ja- + o, 3oD U<-JI ct-t; === c) LAA-OI a..-,0t.4t-J (J, ~0 UA.-Oif/_;_f::::;t{) ---~,- +- O, 3 ULO/ alo~ s + SDO ~1 &J~ ;~! cu s~lt.€~1 Q == -f- Q. 3CO~/ CHy 1~/CIIf/ J, (e) How many compounds are present in the/container? -/,r r1 VI./V (f) ,' C6S b on d; lox;dk!_ ( Wa.} I t!OO ~1 -AJkl -==- ~ ~~Cd I~ s (d) How many atoms are present in the container? €), Odd y /0 eJ3 ~ 'f u-w/ x G, 0;;:; y 10 ~3 -==- ~c( ~ ~~ ( -== cJv 0 '(l ';( /OJVa./v14j )- Cifc; What is the density of the material inside the container? -1-o-1, + 3;),ooci ad- O.dAJo .v<-.:> IjJ 1U<-<J 10d = r>'1 tZY:> o. 300 Yt<-O/ C'l/y /;, Ol/ tjCUd- _ fut<J( &d - (g) What is the pressure inside the container? nJo+ == PV-::::: i ovo VKDI n 12 T P== h((T_ v lfL/,0?J~ I + 0, 5D D1'1-W CJ0> 1u.w1 &::>.:l. d-== + 33. d:J 0 ~ ~ ...3 3 · d ;).\L v I{)L -t ooo ~1 )l o, 3 ? c;:t~ • L o&J at~~, k' x IOL / --=,.....Jd ;__. J13K_ 2. ( 12.5 points) Complete the following table. Name sulfurous acid /odrne ammonia !Jf(:; n/lr;ck_ {luovldecalcium peroxide ch lorc_-le_ potassium hydrogen phosphate ammonium sulfide hf -lvr;ef1 dJox;dL_ manganese(!!) sulfate 11) o CQ_ lr;:_ I e__ calcium hypochlorite IV0&1 So3 (q) IF7 fi11(1) lead ( Ha he11a_ {IUAj rl ok aluW~/num s/lv-er- Formula (tt) oxi(/Q____ AlN SnF2 Ca._ OaAgC103 kc;..!-1 p0'1 (!VIly);; S N02 Mn so?' Pb(C2H302)2 Ca. (oc!)dFeO 3. ( 12.5 points) Examine the following list of chemical substances to answer questions (a), (b), (c) and (d). )C KMn04 X -== ion;c_ (a) Which of the substances contain(s) a polyatomic cation? (b) Which of the substances contain(s) a polyatomic anion? (c) Which of the substances contain( s) both ionic and covalent bonds? kMnO~ (d) Which of the substances contain( s) no ionic bonds? 4. ( 12.5 points) Trinitrotoluene (TNT) is one of the most commonly used explosives for military and industrial applications. It is a compound of carbon, nitrogen, hydrogen, and oxygen. Carbon occurs in two forms: graphite (the material in "lead pencils") and diamond. Oxygen and nitrogen comprise over 98% of the atmosphere of Earth. Hydrogen is an element which reacts explosively with oxygen. Which of the properties of the elements determines the properties of TNT? Briefly explain. None_ G-rtLfk_:k_ (C) I (AI~) ek (].J: e_ e !e. do JNLe > c/,"c;I'UOnd (C); n/ lvvcrn oxyJ?-11 (jte1 ( 0~); r Y'VLe f_,/- (1S l vt/ c.s ,Sl//:; --5, f t<:.. 0 ~t/6:1~ nee_ .s w;fL · fvo;e::-hed a.-/or.-uj J o( hydroJe11 ce .S hc<-v-e... CVMfwwd-s, o{- d;(fos-eul- -ekWf<?H6 covvt.h/h.f2 r;(. 7k.. 1):./c;_ylho£ C2-_loru.J are.- dQ~Y1"1tn.e6 ~ pr-o~-1-led • o{ G- cJ03 ( f~) of- pYGfei /{e. S J-Wfl.: I r? (J -/o c.. COvv(JOUIIr/ CLre. . eke ~u-,'cc_/11 COJ4j /;;/ned! /s I.X/kc.. -1pc;rrtCt1/t2r CCYnfOUJ?d, 5. ( 12.5 points) Fill the blanks in the table below. Formula -.5 u Name Lewis Structure '0• (single structure or II 6 several resonance . , / , ~ structures; : Q. : Q, ', Dots & Dashes Style) f I I(; I e.. /on G .. I' :o~ ' .. s---o: - Or ;o• · / • • : o·.. 0 3 re sont£ r1 02... s --1Yvc£..rtj ( e a c t, (.{/'/ 11 OLA.e Number of Atoms a ou!:Jte 'I Number of Protons 6£ Number of Electrons Number of Valence Electrons Number of Bonding Electron Pairs Number of Lone Electron Pairs Formal Charge on -3 ( or 1.J ) 13 (Or !cJ) --!-/ ( or 0) Su!PttrAtom Oxidation State of SulfUr Atom Electron Cloud Geometry Name of the Geometric Arrangement of Atoms +'-/ -fel-ra_ fu:_ drc:_/ Sketch of the Geometric Arrangement of Atoms and Lone Pairs around the Central Atom Predicted Ideal Bond Angle Deviation from the Ideal Bond Angle (yes or no?) Bonds Are of the Same Length (yes or no?) d- /{Jj yes ye_s ~oot<tV 6. ( 12.5 points) Place X in all appropriate boxes to indicate types of chemical bonds and intermolecular forces responsible for the interactions between atoms, ions and molecules in each sample of matter. (You may use the space below the table to sketch the shapes of molecules under consideration.) ~ ~q; ~'?i ~ vo ~ <oo BaCI 2 (s) KN0 3(s) y Na2 S0 4 (aq) X H2 0(/) 'I ,o~ ~b'? <oo ¢:>~ ~0 ~ ~v ,o "!-..q} «0 >< 'f X qj 0~ )( HF(aq) 'f CS 2 (/) y OQO ~?§ ~ ~ 0~ ~ <( X X X 'I y HCI(aq) (f ~~ (.,e,'? 'f X Br 2 (1) . ~q e,'? <::>' ~(J e,~ 0 r§ ,~ y NH 3 (aq) ¢:>~ i!>-~ ~ .(., ~e, .o~ cj' x X y X y X y y X )< X X X ~ X 7. (12.5 points) The following diagram represents a cross-sectional area of a steel tank filled with hydrogen gas at 20°C and 3 atm pressure. (The dots represent the distribution ofH2 molecules.) Which of the following diagrams illustrate the distribution of H 2 molecules in the steel tank if the temperature is lowered to - 20°C? Briefly explain your choice. G.. • ® (B) (C) (D) owr wf/1 ..s-H/1 be- (JCZ-5. (h-ue Is. o~ h():;j IOvV bo:l,-;'-J fo/nf -!htUv .subskuu:_ -ftut 1-f1ydYOJel1 : heliuM. (If.;. boi& a,'f.Jok; He- 1 aJ-- f{J. 'lk.) 8. ( 12.5 points) Relative humidity is the ratio of the pressure of water vapor in the air to the pressure of water vapor in air that is saturated with water vapor at the same temperature. Often this quantity is multiplied by 100 to give the percent relative humidity. . hum1.d"t re 1at tve 1y = ooo/ actual partial pressure of H 2 0 x 1 /o ~1 pressure of H 2 0 vapor if sat' d ~ Lj/), Suppose the percent relative humidity it8D.Q%\Jt 35.0°C. How many grams present in each cubic meter of the air? ~- p/{;.Q = ( p V - l.j (}, d. n _ YJ K:,-/ t f, 0014-1:?-== /, {7) X ~ 35 Hd-0 /!J 33, 8 0. /5t:trJ = Y o + ;} 1 J -= 3 i'VIM h-1 1'11 /It _ ofwate~e if og K /OJ L = pv h Mf<-1 J nfC / (33.8 /::rro) ~.~-.,_., o~ ) / Q, ObeX b 3 a~. L k 0-<-.1/. 1.oox1o L= >( )( 30.& 1 96 rw:J/ 1 v y jf;, f... Od. /UL<J/ 9. (12.5 points) Ozone, 0 3, absorbs ultraviolet radiation and dissociates into 0 2 molecule?and 0 atoms: ~ ::___~· /(x Q 03 + hv ----+ 02 + 0 tcJ A 1.65 L sample ofair at 22°C and 748 mmHg contains 0.25 ppm of03. How much energy, in joules, must be absorbed if all the 0 3 molecules in the sample of air are to dissociate? Assume that each photon absorbed causes one 0 3 molecule to dissociate, and that the wavelength of the radiation is 254 nm. (fl/8 /760)u:_& X /;U.,J I o, o b7 og ~1 Q, 8 x-- 1o 6 I /:( s- = ==- /, 0 I _ (6. ()de; X X(0- d 5'1 (Jf YI0- 8 ~~ /, /, b 1 7 y I() = 6SL cJ9'5K x /706JO£a-&,,L- L/t ;, -g )/UA) I ;; X (G. 0 d.) y ( (} J3 jM.V~(', J.<L.-0 I)= 10 I{ ~-UVIcc, 03 3 '1J, S) x(J, 60 Y/0£ 111/S) = >( f, 6:JS x;o- 19 10-9 fYl J \x /_1. O/y/r/6 j.M-{Jiec) = ~!.ec..) \ ( 7. 6:15YiiF ;r _j_ 7, 90 X /0-- 3 J f, . 10. (12.5 points) Consider the reaction of combustion of propane, C3H 8 • (This reaction is used in barbecue grills.) (a) Write a balanced chemical equation for the reaction of combustion of one mole of propane. All reactants and products are gases. (b) Calculate the enthalpy of the reaction using the standard enthalpies of formation. A.l!rxn =3 Yl<-0 - [ ~I) -+- ~I) (~/ (-10:5,65 ~I)] = - ;}OL(3~9 kJ I {- 3'l3. s- 'luw/ (- ;wt 15 (c) Calculate the enthalpy of the reaction using the bond energies values. f-t H rf ?./f7_ kJ I ~--- - " -r - I H -c - cI c I I H f-1 ('J-f 'IIY kJ/wN/ o=c~ -1- 1 JM,()I O==o ~ 'lrtkJ/w.J' .; If, o ~ Ll0 il kJ/tuol 1-1- 7c;q o- fl ~~ d f«{)l (37'1 !:::/) + g;~l ( Lfli :.:,,) -T s ~; ( t(9& g() [ 0 ~1 { 799 tl.,1 ) -+- g ~1 ( Lf("c;'~ j = -dOlO kJ (d) Compare the two methods of calculating !lJlO rxn· Are the results of calculations similar? Tiu. '/ as-e._ ve.ry .5eCOMd ~-ft-od /f iS .beldRcL close_ -lo /5 ;/-1)/:)lzb le on o-1~. Th.L less occ u.s: ale be c~ eacl._ ove.r~ valws of bohd e~ylej (e) Why all combustion reactions of organic compounds are exothermic? Explain this in terms ofbond energies. ( OV-eS~ VCdt/e.5 ~ C-C J C -1/1 e/c/ ) bo14d.s -f;o~A-t ma11y dlf/e renf- Y'U-0 le Ct-tll'J exo-fW m/c.... -ILrL -ftuz_t-1 bo"'dj -1-tuL I YJ fh_ h.?t-t d'.s fYOducf:J !n -IWL a_re_ Ye tr c fa be cCLu.JL- .s£.or1F 1-16 , 11. (12.5 points) It is difficult to prepare many compounds directly from their elements, so M-?1 values for these compounds cannot be measured directly. For most organic compounds, it is easier to measure the standard enthalpy of combustion by reaction of the compound with excess 0 2 (g) to form C02 (g) and H 2 0(/). The standard enthalpy of combustion of n-butanol, C4H 100(/), is- 2676 kJ/mol at 25°C. (a) Determine tJJ-101 ofn-butanol. (Hint: Write the thermochemical equation for the reaction of combustion of n-butanol.) A II}) o Y kJ/UMJ/ if/[AA>/(-393.5 y +- 5<AAAJI (-r!)g!;,g f:: 1) s - zs 8 d ( 7- b - If X 3 C/3, ~ y ::::: (b) ::!,1) -,;)g5,g -3 73. S 5 !) X I 3[) 1 - Write the thermochemical equation for the reaction of formation of n.:.butanol. 'fC(s 1 gye;_thfle) +- SH.2(JJ + .Lo~ (!JJ -+ Cyll;oD (r) ·t;./-1-=:-Jdf b~anced 12. (12.5 points) 8.00 g HCI is allowed to re:t with 10.0 g HNF 2 according to the kJ chemical equation given below. 3 HCl + 3 HNF 2 ~ 2 ClNF 2 + NH4Cl + 2 HF In the course of the chemical reaction, only 15% of the limiting reactant has been consumed. Determine which substances and how many moles of each will be present after the reaction. r;;s, or; ttc; c~· <(~~~~ ::) 0~ d./9 m4/ cx:>n 5 u vvr (? d I n/l,'a_/ HC/ Q,/8Cf~/ HNFd 0, :; ;q C! !JFdA/fly Cl 0 1-1 F Cha;r- U<.V ~I I - - 1-/nc/ 0. lb'l ru-vl (), 191 ~; O, OcJtvuol (), Oc}gvvvo/ + J X o, OJg JMAJ! 3 0 w-vl +l§y. o, (/~l -+- '3 y o:Jt ~ 1 o. 0)8 /AA-J / (), o ICJ UtO I o. 0093 /MAJ/ ()I (' l 9 t-vt.<J I 13. (12.5 points) In standardizing hydrochloric acid, 22.5 mL were required to neutralize 25.0 mL of 0.0500 M solution of sodium carbonate. (a) What is the molarity of the HCl solution? c)HC!(q) + dd. 5 );vfL ;1/~~C03 (cuz) ~<)!la.Ct(u-e)+ ~O{J)+ ~ s-, OrnL Q, CJ5VO M G:J.(j) ~---·------------ ?M ;,,) 5 M o, VtA-O( Ill M (b) How much water must be added to 200 mL of it to make it 0.100 M? -~· Iu !,·on (!'1: c 4r -= C{) Dr /II H O, /07} M -== "' ~1 fr I fiw.z/ vul~ of c(;luled so/11, = doO .... L xl,/1= d-ddfv1L a( vu/LPUA-t- 1,(/a_ler addecl == ~dd VJ.-tL- -d00¥1AL ~ d.dYt--fL:;~ 14. (12.5 points) , An 8.129 g sample ofMgS04·xH20 is heated until all the water of hydration is driven off. The resulting anhydrous compound, MgS0 4 , weighs 3.967 g. What is the formula of the hydrate? (a) What is the formula of the hydrated salt? 3, 161g (] 8. -f- O,D3d..96 1~1 f,ooo~l /;)0,3?J !Jtt;J - 3. 9b~J = i.lb1J (b) What is the name of the hydrated salt? /Vt<.-O! /8.0~ 0, ~3096 ;uo/ f. 007/A.<.V I 15. ( 12.5 points) The unit cell of graphite is shown below. The cell volume can be calculated using the formula: V = ..J32 a 2 c. Calculate the density of graphite. r! (_f ~·! b < r o-/ cas- bo YJ a +v~s f~ c.elf : 8)( _L g ~ I u tJ. -f· V? If (d. '-lb. ~ 3, S/8 de nsr' 7= X rd- L(Yl +f~ ~ I /0 -ftJz__ - I XIO-Io C -;J:!; wt) d ( (10. g >< IO- IVc w) ==- CWJ 2> yv7~ of ~ Ut<-:L _~If VO /u ~ ~ -r I VVI ~ 0 UU-!. f 02// -~. y:- '----v----./ J volu ~ r2_f I ~ --{-c) = oj lh__e_ uu.:.l- of! ·- 16. (12.5 points) Using the half-equation method, write the balanced ionic equation and the balanced full-formula equation for of the following reaction. (K+) 2Cr20 ;- + (Na+)2SO ~- + (Ir)2SO ~- ·~ (Cr3+)2(SO ~- )3 + (K+)2SO ~- + (Na+)2SO ~ + H20 oj-(a..t) + IL/H+(rLf)+be ~ dC(+(a.z) J< I Cra Y 3 soj-(cuz_) ~ 1-(;0(cj CrJo;-(at) ( -f J_ · k+ + CZd + 3sc5-(t£t) - fo T- ffa. 0 (c) .so~-r~) -+ :2 f!+(~)-rde- + 811+-(cc_f) (; Afa_f + if so~.srzcfa.for- /oU:J j -r ~ :Jc)+(af)+Jso;-(CZ£)+ -e act .sic&__ + 'lifo 0(9 ~ Crd 07-- (6-'l) + J !Ja.J.s03 (6f) + l( Ha,SOif (~) ~ CtJ. ~Oy) (f2£) -rKJ- SO~(ar,)+ 3 -r3Aic_a.so'~(~) +tf/6.0(t)