exam 1 - 93, '. «Cw ‘ o‘i stem 1. Multiple Choice (30...

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Unformatted text preview: 93, '. «Cw ‘ o‘i stem 1. Multiple Choice (30 points.) 1. Clearly circle the BEST answer for each of the following questions (3 points each). A.) From the decomposition of ammonia gas, one can obtain two different gases, each of which is a pure substance. Using only this information, it can be said with certainty that: a.) one of the products is an element. b.) neither of the products can be an element. @ammonia cannot be an element. :1.) both products are elements. e.) gases do not produce solids. B.) A 1.00 oz piece of gold (density 19.3 g/mL) can he hammered into a sheet which would cover a 100.0 ftzarea. How thick would such a sheet he in cm? (hint: 454 g m 1 1b, 16 oz fl 1 lb) . , Mb 454 [ mi. ch3 a custom W3"... : mew A b.)2.11x10':cm 3 I63. 33 m. hi c.)4.02x10' cm 2 [2‘ "z— . 4c a. xlO 5L (1)432); 104cm .: iAlgierrf? ‘00 Bi XLTJLLB A 2 5 "j : Ci»,Zq cm I e.) 6.33 x 10‘1 cm We”) 7' {3* I in Cll‘l x mil . C.) Which of the following is a correct feature of the nuclear atom proposed by Rutherford? a.) All atoms of an element have the same mass. The atom is mostly empty space. E c.) The number of neutrons and electrons in the atom are equal. d.) The majority of alpha particles to strike the foil “bounced back”. c.) More than one of these is correct. D.) The natural abundance of calcium in the ea‘i'th’s crust is 3.4 % by mass. How many calcium . atoms are present in a 1.50 g sample of the earth’s crust? 23 1.5‘Qficm5‘l‘ KM X imaico‘ x QDZXJO mats __ a.) 6.6 x 1023 atoms t b.)3.1x1022atoms W3 3 0"” $0033 C‘s (mt Ca. C @737 x 1020 atoms d.) 7.7 x 1022 atoms 1 o e.)5.lX1021atoms $7. a m cit-cm. E.) The element M forms the chloride MC14 containing 75.0 % C1 by mass. What element is M? a.)sodiu1n Mean-{5) - 0.75 b.) potassium ‘ X D C @titaniurn d.) osmium ~ e ) mercury 1: K O. 3H)— 3 X =‘ fscmgjmt —» Hesse“) 5 Wag ‘ r473! F ) What volume of 2.0 M HCI is required to dissolve a 10.0 g piece of Zn? Zn (3) QHCI (aq) e chn (aq) + H2(g) ‘3 OmLfl B {nag-962% [moi an 9?.0 mol H Cl \Lw HQ! _ c. m i/ (1. 31011114 is; 330 mL {:50 ml. +0 52 5‘6 {:39 G.) Predict the outcome of the following reaction: (21280.; (sq) l. NaOH(aq) -) ??? NQZQO ti (ML) ‘l‘ Cu (0H); {5) no solid forms, Cu(OH)2. A b.) one solid forms, NaZSOzt. ' 0.) two solids form, NagSO4 & Cu(OH)2. (1.) no solid forms — there is no reaction. H.) If each of the following solids is teacted with hydrochloric acid, which will form a gaseous 9 . product Basoa {9 must we Bauum + H10 m + I. atium sulfite { & “Ll Ii. zinc oxide X 5 02 t J 111. sodium bromidex 5 lithium carbonate a L; a a.) I Ltzcgama-QHCIQ‘Z) “‘1 + Mao“;- CO; (5) b.) H (mm c.) III d.) IV more than one of these will produce gaseous products. I.) A new super-secret pharmaceutical, referred to only as compound X, is in the final stages of testing and a chemist needs to maximize the amount of product X formed in a reaction. In the last synthetic step (balanced reaction shown below), 0.0050 moles of compound Y are used up to make 27 mg of compound X, which has a molecular weight of 237.8 g/mol. What is the percent yield of this step in the synthesis, based on the chemical equation below? 2Y + excess acid *9 X + 2 H20 (1) + 3 salt a.)2.2% b.)2.3% c.0050 moi fix/K M X 2.313% $0.56?st C 20:01 y lmel X ~3 (tobacco $100.: 6% jeeld 1‘ m X “30 : '1‘ 5‘ Wfih‘w 4 0.5% 8 ° J.) Determine the empirical formula of a compound with the following mass percent composition values: 44.87% potassium, 18.40% suifur, 36.73% oxygen. Name this compound. .2. 19-05 is ompound is potassium sulfate. Eta-TF3 O x “WI 0 -_ “Mg 0 a; 0 n .) compound is potassium sulfite. 16.00:} 5 ‘ 5 “*3? A 0.) compound is potassium sulfide. ‘ l I Lf ? c.) not enough information is given to determine. 443 73 ‘4 xi“: t“ ; ' ma K ‘ :2 C . 34.1013] " ‘ , . . e 5 ? _ a 57 3? .‘ £5403 5 )q “M S ssh—~237pr 5 1 " - S7 ‘- Calculations ‘32" 0qu S g?— K2 3 Chi 2.) (10 points) You are given a sampie of a magnesium carbonate hydrate, MgC03 .. x H20. You weigh out 14.5 3 g sample of the hydrate and place it in a porcelain crucible. The sample and crucible weigh 18.01 g. The crucible w/ hydrate is then placed in a 150 °C oven for one hour. (Note that 150 “’C is NOT hot enough for thermal decomposition of carbonate). After cooling, the crucibie and solid weigh 10.51 g. What is the hydrate coefficient for this compound? You must show work for any credit. . A +XH O . .~ ‘ —-—«$ ' c5 2‘ i " - ‘ 5 answer: 5 Workspace: 18.053 mamas Sour! afiw ions: an)de v wkigg’edus Mb A5 ML“ 4-0/- 3ng Crucible 9/ . 1.03 Ms ciqu » - g VSotEd “ qjcej (flap-Solidufmnlffimfg .+ 2/ f. 130 (,3 Mamet/43d T inei “3/0 I ‘ 36733 ixtaop-KWH t oftlcg my Mac A“ fitfiq N 5. .0! N ‘ ..... '8 3 to .0qu L ism)! HjCOB “sea H CO« M .. .ogs mot H LO:- 0 3 5X gqfigga-HJCOB 11 i .085% 3.) (10 points) An iron ore sample weighing 0.9123 g is dissolved in hydrochloric acid and the iron is obtained as Fe?“ (aq). This 1732+ (aq) solution is then titrated with 28.72 mL of 0.05051 M potassium dichromato solution. What is the mass percent Fe in the ore sample? Titration mm: 6 Fe2*(aq) + 14 H+(aq) + (Cr207)2'(aq) —> 6 Fe3"'“(aq) + 2 Cr3+(aq) + 7 H20 (1) Answer: 9 . = t AFemore 53.23020 Works ace: r" 1+ " p m ‘17: Ft {5) £23.72mL K H’ W” (Smoi IZQZJr X 55833 rear O-Lfgélj X X .,.. . 103M, IL. [[email protected]?)2 tenure.“ 853'” 0.4%! Tia?" Uh SW‘“ 9%me 2*: 8 Ktoo»; , 000123801“?— 53.18°?O alga aka... W 4.) (16 total points) The use of iron an abundant element in the earth’s crust goes back to prehistoric times. One method for quantifying the iron concentration in a sample involves three steps. The first step is to dissolve a portion of the free element in concentrated hydrochloric acid to produce iron (III) chioride. Write a balanced equation in the box below for this reaction: (4 points) (a) Reaction I: ‘6) _—-‘r afieujmz) +3H Q‘Fefs) HSHCJM 213) The second step is to reduce the iron (III) chloride to iron (11) chloride using zinc metal. Write a balanced equation in the box below for this second reaction: (4 points) (b) Reaction II: QFeC/lamm + Zn”) “‘igi‘éC—fiafacé) 1‘“ Emma) (cab) The third step involves titrating the iron (II) chloride with potassium permanganate under acidic conditions. Write a balanced, net ionic equation for the following redox reaction in the box below: - H 4 +3 «3 Fez+(aq) + (Mn04)‘ (aq) —> F8203 (s) + Mn2“‘"(aq) ‘8' to e c (8 points) (c) Reaction III: Work space: ‘5 jag—h 1+ 51— 36 + i % EHJOQY Ha (ML) "i 1“eta/09(5) i” g“ (“1) + i O H9 a _ *- g X if XHLZ)#(M”G‘1)IMH d—i aHnata %) i“ [7X “2/0 (it) to 192+ ' r r7l+o "a 5520 6 (a) 7» 3(5) ““tl 5.) (14 total points) a) (4 points) Write a balanced chemical equation for the combustion of ethene gas (C2H4). b) (6 points) Is the reaction written above a gedox reaction? Which element is oxidized and which is reduced? Provide oxidation numbers to justify your answer. - oxidationii weft “W 0 WWW M 02- e) (4 points) How many electrons total are transferred in the balanced chemical equation in part (a)? I $1 Answer = I electrons E 6.) (20 total points) a) (5 points) A 6.143 g sample of solid Ti(OH)4 is added to 85.4 mL of a 1.098 M OfI‘INO} Write a balanced chemical equation for this reaction. b (4 o oints) What are the names of the reactants? c) (6 points) At the end of the reaction, is there any solid Ti(OH)4 remaining? You must Show work for any credit. m Moi 0H W “hat TJOE—DW L? s! OHM JIQG V . - se—taj West, x “.1 .3 0. deH W x I15.‘?I(j THBHLI, imel TEEN)“: ‘NZD M6” > a mg! H 1" . l H t“ ‘ a l L i 0 c s t Maze ? Circle one: 3 there is solid remaininj id’s-ll. H N03 K x émsi satiety; mantle I L, K EWE Ema“ Ht OR NO there is no solid remaining. J- L91. (1) (5 points) If your answer to part c was yes, calculate the volume of concentrated HN03 (8.15 M) that needs to be added to dissolve the remaining solid reactant? If your answer to part c was no, then calculate the maximum amount (in grams) of additional Ti(OH)4 that could be added to the solution before it stops dissolving. You must show your work for any credit. "“ ‘l' was“? Hm“ M? Heron?) 0.9520 met oH‘ “0.0‘15t’t mefiw‘ 3 7 —~ K 1M W 1 ,,. augment: it. x seat- W Answer: f‘i l 5 mL HNO3 needs to be added to neutralize excess base g Ti(OH)4 needs to be added to neutralize excess acid ...
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This note was uploaded on 10/03/2011 for the course CHEM 31 taught by Professor Roberts during the Fall '10 term at Lehigh University .

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exam 1 - 93, '. «Cw ‘ o‘i stem 1. Multiple Choice (30...

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