quiz2_key - Chemistry 114 . Quiz 2 Fall 2007 ame: You must...

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Unformatted text preview: Chemistry 114 . Quiz 2 Fall 2007 ame: You must show all of your work and use significant figures. 2 or 03 1. What current is required to produce 4.0 g of metallic chromium from chromium(VI) oxide in 24 hr? ' L ' ‘ (41318) Q: 1%? H43 “Viz/“gr her: m/‘WL WM: 5qugi 7., 1%.: L“) 5 619%".338 ‘ ,- 5 Jo. (5\.Qq(el‘( ’~ Q MMVWWW» 2 0.515744 =7 05; Q/mPe/FCS 2. voltaic cell is based upon the following half—reactions ' RED» — Ag+(aq) + e" '—-> Ag(s) 1 8° =0. 799 V m — Cu?+(aq) + 2e‘ —> Cu.(s) £°=O. 337V Does the cell potential increase, decrease, er remainthe same when the following changes occur to the standard cell? (Show your reasoning) a) Water soluble CuSO4(s) is added to the Cu2+/Cu half-cell compartment (assume no vol- 21111:; hange)‘ lflaJ‘Lle Mb‘r 43' lfigis) «r (Laugh? ‘I R: 7.03% / Diff]; {Mr} ’1‘ a RT :7 AB: lurk Mimi/“Q, l, M585 1" b) NH3(aq) is added to the Cu2+/Cu half-cell compartment [NH3 reacts with Cu” to form Cu(NH3)i+(aq>1. (1 pt) _ ‘ [CM/ml ‘3! “*7 ‘Q 4% *5? AC Lamasefi c) NaCl(s) is added to the Ag+/Ag half-cell compartment [Ag+ reacts with Cl‘ to form AgCl(s)]. (1 pt) 19(34‘34/ :5 GOT 1’7 A 8 cinemases (1) Water is added to both half—cell compartments until the solution volume is doubled. (1 pt) 2" lath/all .. ; img r» at :7) M: Fifi-W565 [#36111 a“ [Asll e) The silver electrode is replaced with aplatinum electrode. 5° = 1.19 Vfor Pt2+/Pt 1 t v . i ._ ' K + “i ( p) NC air: ,5 fiwwm / Pt to meet @NEJ A3 ed, r E. E If} ’, . . , A t 1, rm,va Em ‘5’ A3 (5‘) WV @540 C5 -2- 3. Consider the following half—reactions measured at pH 0: Brog(aq) +‘6H+(aq) 4 5e" —> 1/2Br2(l) + 3H20(l) 80 Br2(l) + 26' —) 2Br'(aq) - 8° 1.52 V 1.065 V . a) What are the products of bromine disproportionation? (2 pts) .‘ grab” owl» Br I b) Will bromine disproportionate spontaneously at pH 0? Why or why not? (2 PtS) . A eating; a» was. — 1.52, z — M55 4 o :77 M mi; plpwcbmm c) Which is the stronger reducing agent at pH 0: Br'(aq) or Br2(l)? Why? . (2 Pts) emu/wag! Manta aw has fiaw impala/qu ‘56— be Wig; W than) “Er be wévlbebbeil er'aevg) a: —- Lees Q me, mug) a; 4.5a, :7 Br‘ 4. Give each balanced half-reaction and then balance the following oXidation/reduction equation in acidic solution ’ ' ' Jr b ' ‘ QJ 4’ 37 O crzohaq) + CH3OH(aq) a Cr3+(aq) + CH20(aq) (5 pts) on: 035% —-—7 was; 4:“ ac?" RED". with?“ J? G e; «7 Rafa»; W *¥“*._. w. a» MW" “l” Till;an cu w t E «:1 W W “me 5 :3 a?) v > (Kg-9%» 1mg; + NH" {a5} aim?» ‘47 lava“ ('11)) V “film Qvlb?l’h6\* gfl'tlfibll Cap + KW (16\ W3; 3L0? (it? 4» wage (up in 3’ the {a} Chemistry 114 Quiz 2 Fall 2007 Name: Youmust show all of your work and use significant figures. 1. A current of 0.0100 A is passed through a solution of a rhodium salt, causing reduction of the metal ion to metallic rhodium. After 3.00 h, 0.038 g of Rh has been deposited, What is the oxi- dation state of rhodium in the salt? ' r @049; Egg. fie; X1: [fiexvh '1 Wm“: Witch” EGQflBSS’ ;, fl wit W l 9* Qtfiasbw . D‘O'E‘g ’ 0.9mm “Rh” mm 2255‘ ‘- t 0,0903%»? X3” , {Shfimi‘rfilwi’t 2. .Give each balanced half-reaction and then balance the following oxidation/reduction equation - in acidic solution.+3 . VP? 444 +1] H2C204(06D + Mn0;(aq) -> (mg) + Mn2+(aq> (5 pts) ox: 143.06,th «*7 maybe,“ QED: mm; + 5e: .7 mm” ........ 5 (“@09qu Lag) ---‘l 3) ‘1 (Mnth (L6) + gH'" (L6) +5@;.,.7 > unity 4/ 94*” (00 V” my?” (if; L Li H3003 £10“)th 4' GH" a )0 eogtgj t a m3“'tt€)\ L «Eula if) -2- 3. The following reduction potentials were measured at pH 14: 4H2Pogcaq) + 4e" —.> P4(s) + SCH—(aq) - Ve" 134(5) -+ 12 H200) + 12c" —> 4PH3(g) ‘+ 12 orrmq) 5° —2. 05 V —-O. 89 V a) What are the products of P4 disproportionation? (1130 Hayoaj M P143 _ b) Will P4(s) disproportionate spontaneously in basic solution? Why or why not? 2 > V V a ( pm) hemp: .~,Q\%9t~(va.0:>) 2 mlojo :7 apmitmmke 0) Which is the stronger oxidizing agent at pH ‘14: P4(S) or PH3 (g)? Why? Wm waw' aw? “M 0b 1 (new . Mée ‘9’ ., m“ 0‘“ _ ‘ . x ' 0 . PR”? “33303:, f, v 1.05 ') P2453) l)“ ,) :. 036i :7 _FH5 4. An electrochemical cell is based upon the half—reactions: . Mime“ fax" 1) Cd2+(aq) + 2c- -» can) 5° =—_0. 403 V MT“ £ng 2) Ni2+(a‘q) + Ze‘ —>_ Ni(s) 80 =—0.,25 V I a) What is the spontaneous chemical reaction? . ‘ - r \ l . ' (1 pt) .asigctf? Jr Qfl53 «:7 {o‘cQt {5%) 046' V. b) What is the standard electrochemical potential of this cell? I? '1’} apt) Ma; gvmwyc Cwmxt 49.95- (493053: 0453 c) Electric current in the external circuit is due to a flow of electrons from 1) to or from 2) to l) (circle answer) ’ (1 pt) (1) If a salt bridge containing N aNO were to connect the two half-cells would the NO§(aq) ions move from 1) to 2) or ' (circle answer) (1 pt) . e) What would be the effect on the potential if water were added to both half—cell compart- ments until the solution volume were doubled? Why? X 241 I I (1 pt) .6, a, at 9.995? «t, CL in?" are an fl tea a a We ~ M: awe 61 mt Elvwgi f) What w be the effect on the potential if water soluble NiC12(s) were added to the Ni” half—cell? Why? (1 pt) ~57 RV :7 AC tltceemsw ...
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quiz2_key - Chemistry 114 . Quiz 2 Fall 2007 ame: You must...

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