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exam_answers_Exam_1_key - Chemistry 142C Seat (1) Name E l...

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Unformatted text preview: Chemistry 142C Seat (1) Name E l Autumn Quarter, 2006 — First Hour Exam Lab/Quiz Section (1) October 20, 2006 VERSION A Lab/Quiz TA (1) 1. (8) Give the complete chemical name or chemical formula for each of the following chemical compounds: (a) Ammonium Chromate l N H Z L4} (b) KBro3 MM lo YD \M Wit, (c) Lithium Hydrogen Carbonate lg]. Hi '40; (d) CaatPoaz WEE»— (6) Magnesium Nitrite Mg ( N D» 2 m M ‘H, l (f) NaHso3 SD lUL (g) Aluminum Sulfate W (h) Cr(C10)2_CI\flmllAm_L_I_LJ_hAI,PQLfilO\/li‘é v 2. (9) Give the chemical formula and name of a simple binary compound that could be formed from the following pairs of elements. Formula Name (a) Phosphorus & Bromine 1 m (b) Magnesium & Oxygen 2 ‘ 0X! (0) Gallium & Nitrogen [\l m i 3. (8) Calculate the molecular weight of each of the following: How many moles of each would be contained in 50.0 micrograms? (a) P4010 MM: 2- eBJ/mK/[loles= I (b) CuSO4 0 SHZO MM: - jileloles= 24212 HD'7 Chem 142C — Aut. Qtr., 2006 — Exam #1 Page 2 4. (8) Calculate the percent composition of each element in 45.0 mg of r ‘ CaHPO4 - 4H20. C (M a } ")0 z 1C” WW} ' 20‘?7-l7/9/m0l ‘61 20%); H.370 ~. 401; 41%: ZO-GI/l 6 [7,CU.UO %Ca=lfl.?2 %H= ’j-EU %P: %o: (ll-g 5. (9) Complete and balance the following chemical equations giving the most probable phase for the products (8, l, g, aq). (a) Combustion: C4H802(1)+__Z__02(g) X l’lCO; + Ll HLO (fly + I; (b) Decomposition: ____Na2CO3°5H20 X Nflzo (33 + + I? H}Olflx (c) Combination: g C12(g) +_Z__A1(S) X 2 A l m 7.) (.5) 6. (10) Calculate the empirical and molecular formulas of a compound that contains only carbon, oxygen and hydrogen and has a molecular mass of approximately 90. g/mol. Upon combustion of 12.0 g of the compound with an excess of oxygen, the yield was—a) g of water and a g of carbon dioxide. @211 HO [MONO [2.3 H wing . /— fl 2 "(9-03 " fig%;5 $1.335momlfliz MEEgH Imle 002" Zak“ (’0; L (W‘le IMO) C c //~ 3 KUM‘ 00; 0.9620mol6} (20le t (“~— lmole VERSION A r ' [U' U ‘ r57 20 ' ‘ ' u 4 C \%§ 1 Chem 142C —- Aut. Qtr., 2006 — Exam #1 Page 3 7. (m Calculate the percentage abundance of the stable isotopes of magnesium if the most common isotope of magnesium, 24Mg as a mass of 23985042 amu, and is fl 78.99% of Mg. The other two isotopes 75 mass = 24.985837 amu) and 26Mg (mass = 25.982594 amu) are the only other stable ones. pz.a;;il;)(v-1W)t WZt-WwW 7! 2mm?) 4%) 0-1WI+X+7I‘ [‘00 Y: 0%ka IM‘IU + 244mm + WWW I za‘flawwszfa/ ‘qumt ': « 0. 0017500 x10.00167y\ 7:04}ng 0 Abundance 24Mg:=78.99% 25Mg: Ei-fiiifiliféMg: l I ‘ /D 8. (W); Calculate the percentage yield in the chemical reaction below if 14.35 kg of 0\ bornite (Cu3FeS3) yielded 7.64 Kg of copper metal. 2Cu3FeS3(s) + 702(g) _> 6Cu(s) + 2FeO(s) + 6S02(g) QM)?ch 312. Maj/mo) H,%5Dj 1 WW (W WSW: W Wj/mol bmvlgc (7an mm} MW 56 3 ZkasCuaFéJ’ [29' ham! CM [26.u7) Moi (M; M 3 Zolooajqflfi quf [moi 0V1 CM pic/Na) 741* a v e 0 a??qu 7754 “ “W” VERSION A Chem 142C —— Aut. Qtr., 2006 — Exam #1 Page 4 9. Q8.) Calculate the mass of hydrogen cyanide that could be produced by the complete 9‘ reaction of 500.0 g of ammonia, 700.0 g of oxygen and 400.0 g of methane according to the equation below, assuming 80.0% efficiency of the reaction. 2NH3( g) + 302(g) + 2CH4(g) —> 2HCN(g) + 6H20(g) W? NH3 \WlNkib Zmol am 2‘7 owj Hw , ,. ~— 3 ' r J j l 3 f WW} FZmulNW; X mum/M ” U015“ 29.02 100 on mom yzmvwmfi glowwwg g V J 3 @362 5 mil 0 L Wm HUM “” ll 7?) ‘ ‘ Waiting two CM W W ,1?» mm M , 3 L” mfilmolv‘rm‘ L\..\0\‘W</V\J “7 go“! 10. (9) Calculate the mass and number of atoms in a 0.0010 x 10“ pico mole sample of 252BS (25208297 amu). 0.0M >~Il?'”117molx 1 ml F 192.0%20175; J/ .____.___ I . x ,/7' W mm . O‘UOWHD'HYW‘Q‘f WM \LKLQ‘LZNW’mM/lb low“le WW : VERSION A Chem 142C — Aut. Qtr., 2006 —- Exam #1 Page 5 11. (9) How many electrons, neutrons and protons would be in a 0.00158 ng sample of 333190” (25910551 amu) ions? 0.001517% ,LLK \mol is? )L ngm, Wq n3 Z'fl. 109613 {moi 1315 V Zlflu Waivwb Wham Ki): [0% quoSwOOfi-lwimmi W “mm am): {Wm/15 [2R lovlwimé: 35272110“ Wm; WUng 1‘ i “"157 mnr m aims at A Imciwiilflb 3 (fl 1 m Wilma I l W RF 5 2/ )1“ é; “twat; P y; 1”" P+=%u%l*l0” , 12. (5 Bonus Points) The element 37 is Rubidium, an alkali metal that is very reactive. What is the name of the chemical element after 36 Krypton? Answer EWM gill“! 5 VERSION A Chemistry 142C Seat (1) Name 1; E Autumn Quarter, 2006 - First Hour Exam Lab/Quiz Section (1) October 20, 2006 VERSION B Lab/Quiz TA (1) 1. (8) Give the complete chemical name or chemical formula for each of the following chemical compounds: (a) Magnesium Perchlorate W (b) NaHso4 (0) Potassium Peroxide __§Z_D_Z_____ V (d) Perseus (e) Strontium Phosphate it”? 1 a)” §2 (g) Ammonium Hydroxide N Dlj: i (h) K2(NH4)PO4 thfiwmfl 2. (9) Give the chemical formula and name of a simple binary compound that could be formed from the following pairs of elements. : Formula Name (a) Carbon & Fluorine E (E, t Him I p (b) Calcium & Nitrogen ( g; a N 2 Calf/NAM hi (c) Boron & Oxygen Q§____.__ 3. (8) Calculate the molecular weight of each of the following: How many moles of each would be contained in 75.0 nanograms?-—e-—‘-r [5 : 10*“ “6 I I «0 (a) N205 Moles: x D I (b) Na2c03 - 10H20 MM=2&M15% lmoi Moles: 2 -u;:% H2"D . Chem 142C — Aut. Qtr., 2006 —- Exam #1 Page 2 4- (8) CalClllate the percent composition of each element in 45.0 mg of Na 7: A ’pp :_ NaH2P04' 2H20- 1 NWZZ-OM 19m [7‘7 0/0 j, 17 2 WOW , u 0 1 fill-0 %Na=lj.f1 %H= 347% %P= lolfl %O=_(Lli_ 5. (9) Complete and balance the following chemical equations giving the most probable phase for the products (s, l, g, aq). (a) Combustion: _.QH302<1)+_"l_02<g)X hwltj) Jr Lily)th (b) Decomposition: \ 2- NaHCO3 °5H20 Z N“; O L‘) Jr loozlj) f H ‘47}le (0) Combination: L F2(g)+_____Si(s) X S l Fm L3 ) 6. (10) Calculate the empirical and molecular formulas of a compound that contains only carbon, oxygen and hydrogen and has a molecular mass of approximately 120 g/mol. Upon combustion of 15.0 g of the compound with an excess of oxygen, the yield Was W g of water and m g f carbon dioxide. H . 0'1 2 [ . U will»? Hlofi 11m)qu 2mng m) H g / 9 mm W "if—9%? '7me ’ W3 % 2-5 0/05, 21W (,0 X M» Imol C : mm C 5 } ‘l‘i'of’lwpf MO! 001, melmg 7 awac \ woe mo“ W 2 TIMR “Vi—M "‘“l 0: M01] M010 “#030 ~—7*“ g VERSIONB \l 9“le J? 5‘ Z gFIDO") a kaww/ Chem 142C — Aut. Qtr., 2006 — Exam #1 Page 3 7. (Q0) Calculate the percentage abundance of the stable isotopes of silicon if the heaviest q isotope of silicon, 30Si has a mass of 29973770 amu, and is 3.10% of Si. The other two isotopes 28Si (mass = 27.976927 amu) and 29Si (mass = 28.976494 amu) are the only other staglke ones. \/ (owwlmmamp><(27.fl7u0m)+ x/(z‘MWL/‘M : 1907 0. 0310 H MI 7 {-00 y: MW 1): 0- azmum+ 27. WWW «15.07%»? zwwdfltfx >29“) JOHNS—UH = 0.011749“ K 7 0.0117?) \[11 O‘Oqll 2831: “HEW/1293i: 5-1; 9/9 8. (MR). Calculate the percentage yield in the chemical reaction below if 17.95 kg of 0) bornite (Cu3FeS3) yielded 8.14 Kg of copper metal. Abundance 30Si = 3.10% 2Cu3Fesg(s) + 702(g) ——> 6Cu(s) + 2FeO(s) + 6S02(g) mam?) : alzw 31ml nfi'filcj : 17.01603 H.01503 (New? )L M53 U W W I, .57..+molw fling y. 2 m0 lair/3} VERSION B Chem 142C — Aut. Qtr., 2006 — Exam #1 Page 4 9. (M) Calculate the mass of hydrogen cyanide that could be produced by the complete 3‘ reaction of 400.0 g of ammonia, 600.0 g of oxygen and 500.0 g of methane ' . according to the equation below, assuming 90.0 % efficiency of the reaction. 2NH3(g) + 302(g) + 2CH4lg) ——> 2HCN(g) + 6H20(g) 9 L10M NH?) Imol Nib: 25-175nnol , H70 0}: RSWX f) )L 173N139 6’ x How/21 glmol 7720302 /; . n \g (0.03 2 1919 M0\ 03M 20W] HCN 2"] fl _____.. : .0= ‘30 HCM gym“); 54 mm W 357.1716HCNl 00’ \L/j/ 10. (9) Calculate the mass and number of atoms in a 0.0435 x10'3 nano mole sample of 252BS (252.08297 amu). (7.0 bf 65* 10 “’9 nmvl ‘3 5972311?"l Wk; 262159 LfZSHU’MWM Eb l W75 ; lmlEe ' VERSION B Chem 142C — Aut. Qtr., 2006 — Exam #1 Page 5 _. 1L ‘ /’f I p I l 0 7:3 11. (9) How many electrons, neutrons and protons would be in a 0.0175 pg sample 0 352190“ (25910551 amu) ions? >169 WWW HM prvhns, lDDelonVH/lé LWHVMER‘C’L M : (1,7c3r10’” MOI 213 250L109} Maw 10’“ 2L (Lowclow Mo! Kl: ah” l W] K15 : Lf~0Ul7fl 107 min/Vs (Hi ¥F4)nl$tp> WWW!“ ,N=§'g.w»m°' gimme“ 12. (5 Bonus Points) The element 37 is Rubidium, an alkali metal that is very reactive. What is the name of the chemical element after 36 Krypton? VERSION B ...
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This note was uploaded on 07/14/2008 for the course CHEM 142 taught by Professor Zoller,williamh during the Fall '07 term at University of Washington.

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exam_answers_Exam_1_key - Chemistry 142C Seat (1) Name E l...

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