CW 14(1) - CHM 2046 Class Worksheet 14 1. Demonstrate some...

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Unformatted text preview: CHM 2046 Class Worksheet 14 1. Demonstrate some features of a HHS/NH4+ buffer system by calculating the pH of each of the follovung salutions. INN? w (a) Equal volumes of 0.50 M NH; and 0.50 M N34Cl are mixed. . K \ . EamoL~ $45£tuna " oL~LJtLJ \31 l2,-*€>0*2§§h4 :q‘lS-fi "—0 pH: (b) To 100. ml of the solution obtained in (a) above, add 400. m1 of water. wnL%%“ 0;} b1llg 00—? ‘00 : g—ogo qua 0 9570 ..\o . - ____ P“; -\ecj§-E7K\O —-\9fi pH: 01 25 (C) To 100' “11' 0f Pure H20. add 0.015 mole EC]. (g) . (Assume v is constant.) . . A H3O+ :: 0' it 04001. ?H= 49:60-15" AAML W 4A....“ fiV-O bo-szLHLp5= 0469.. (d) To 100. mL of a fresh portion of the solution in (a) above, add 0.015 mole HC1(g) - ‘ + TME- 1430+”? “HS‘aNHH +HLO . ,’ . '5; (3-315— aka—0"; 1 0v: 0?— ' 9 0A (1 MA mm +Y‘— I430"... 14...:th Fug Clix—101m ‘- o 0*‘0 O'W O'IO : . 5’ ~ . , , " PH =M ‘35 WrH Qistseegngw‘13wk H Ashen (e) To 100. mL of pure 20, add 0.015 mole Na0H(s). (Assume V is constant . )r _ - 7- , BEL“):— : Q-O\§mo\~€ ; 0"t00L ?H : V543! PAW M, ml?“ 1;. Q. 7'0 19mm (f) To another 100 mL portion of the solution obtained in (a), add 0.015 mol Naorfls) . pH = 1348' NEE r 0H’+ NH.."‘ ——*7 NH: +HLO :1: 0‘“;- 0.2g “1,: 04S boar—1 flan, a mm at +7._ OH‘ a, C. I . o o l o \o 0 1+ pH = gang's. H: C105 - o 0°10 \ _- P a ._o “MWLH fl (am ISL/L" New VH Wane—M this”? Q13~ fieninLLih—«P M W“ 64" SA OYSB, 1 2. If 100. m1 of 0.10 M fine and 1.0 ml of 1.0 M NaOH are mixed, (1) What are the principal species that would exist after mixing assuming no reaction takes place? (Assume V = 100 mL) hoM i«omt .40th [HAG] = 0-\o M [mm = [OH'] = 0.0m M (2) What is the net ionic eguation for the principal reaction that occurs? After this reaction goes essentially to completion, what solutes exist in a reciable concentrations (a 0.01 M), and in what concentrations? HAL+ OH—Hé +AOQI %:OFO\O Md I oao ovom ,_ , N _.,_ C; -_)&F __jm‘ _%_yL 014 DO {'ankfit a? C 9.00. (0 ‘9"0‘0 -. + .— [g.A;J=Q‘0q M, [No~1=0‘0l0M. [*A<.1=0e010M (3) Circle what type of solution now exists? SA WA WE SB (4) Calculate the pH. PH :- -—- lo ©‘O\ pH = 3. Similar problem, but now using 10. mL of 1.0 M NaOE. (Again, assume the total V s 100 mL.) (1) Principal species after mixing, before reaction: Elofl : EM] : {*0 _L9_ 4‘ 09, '[HAcl = 0-\O M [Na+] = [OH'] = gg-goM. (2) Same net ionic equation. After completion, what solute principal species exist, and in what concentrations? T 3’1: mww Z l__M-_ '% _t_-),‘___ Gm \ao‘iL O H— J'- W ‘ C' O O Orlo [LLF] = 940 M. [No.4] = O=\O M, [ é] a __/M (3) Circle what type of solution now exists? SA WA BufferSB (4) Calculate the pH. at . KEZEUE— :\0 : S-réxlo H Ks» “9700‘s, P _ Eu'] 3 Sg-(omo'iaxoqo CHM 2046 Worksheet 14 - Page 3 4. A 100 mL sample of 0.10 M am: is titrated using 1.0 M NaOH. (a) Complete the table, calculating the "major specie' [...1 values and the pH for several points in the titration. Assume the total volume remains constant at 100 mL throughout. vNaOI-I Solution Contains (principal species) Type of 8011:. p3 OmIg. [HAG] = 0.16M W“ V30 1 mL [HAc] = m_ ‘ [Ac'l = lav-«ko— % ' ‘8' 2;? [Na 1 - Q_O_\_§._A ' fl 5 mL [me] = %%A= . S [Ac'] = MN u h-‘1 CF“. 9 mL [HAc] = J%§§¥T = u q LAC'] = g;_§fir4 . u 52-} Ti/jlo mL* pm” my} = Muzzy] = MM w 3 - 3'- C? 11 1521. [OH'] = _Q[_-N_g_+\_]_M= MAC—1 = QLM stung 11-0 15 mL [OH'] = %Qa§_]_M= Milka] = Q'_\O__p\ 953+ we 0:1 20 mL [011‘] = B-IOM [Ac'] = w ages?) \3-0 [Na'] = fl)»2_:_QM * Equivalence point . (:0) Plot the results from the above table: 149". k’rrr-AQ Ti N‘LOH - o 5' 9 1o 11 15 (in mL) 20 5. Lewis Definitions of Acids and Bases (a new way of thinking). Bases M~ (fi’r‘r’y c A/BReaction: 100 WM M W34; 9.. 0.100?" “NE/“Q veg—kw s + M" Example: HAO +:’NH3 —> RC” _,(_ --NH3> «i— --' 4L ._.. A (i , Jr Isa 1 Ag +- Q 7 j (S) flwflié‘ww‘f ] U" 75 N scab) W2. ‘9 1&(98147- é o In proton transfer reactions, the H+ is considered to be the acid (not the Whole donor 232 i _. such as HAc or H3 0"”). ' ‘ ...
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This note was uploaded on 02/14/2012 for the course CHM 2046 taught by Professor Veige/martin during the Spring '07 term at University of Florida.

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CW 14(1) - CHM 2046 Class Worksheet 14 1. Demonstrate some...

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