3600_Ch13_probs - 13-1. The chelate effect is the...

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Unformatted text preview: 13-1. The chelate effect is the observation that multidentate ligands form more stable metal complexes than do similar, monodentate ligands. This happens because the entropy Change when one multidentate ligand binds to a metal is greater than the entropy when many smaller ligands are bound. 13-2. (Xy4— gives the fraction of all free EDTA in the form Y4‘. (a) At pH 3.50: -0.0 —1.5 —10.24 10 10 ...10 _3I4X10_10 4- : _ O‘Y (10-3.SO)6+(10—3.50)510—0.O+m+10-0.010-1.5”. 10—1024 (b) At pH 10.50, ocy4- = 0.64 13-3. (a) IQ = 06y4—Kf = 0.054x 108-79 = 3.3x 107 (b) Mg2+ + EDTA # Mng' x x 0.050—x 0———'°5x‘§’x = 33x107 => [Mg2+] = 3.9x10'5M I341. (113' -| l'ili'l-"l I: {'LrT'I [11,-4- I‘L'f — 41"}: Ill“ ' .I' 'If'r : [321 Hill L _. _ 1:1;1l. , _ ..1-1,,4 |'J..r.111~.. . _ @1111}. “n. Elna-“1*: ifi'nul-I ._ 2f) :— 1.151}: Inn! 111 :--. I11 ;;.-"+ —. 21.0.1 . . . L1.‘i.[1-. l _ rl.~1 1"; |:I.'Il'.|'li:|| :'u:1:.'u_'n|r:1u:i||til-l n‘r-‘- In If”:- li .[|l.l|:'.l-1|':Il'~'1-]— |..‘-.‘-:-c ll] M {1114+ + |-.l}'l'.-"'-. ~-* fit-‘1'” . 2' 1 |..‘I.I 3- ll: '- IJF r: ill -' .I. 'I _.I .. '_ II: _ liafix IUJWI __ [El-T}. . . . r'.3‘.‘-'-.IiI-*~. is] £301le liuunul :-u!-_I_-I_-nlr:1-.mn L3H u‘r'" H | Hug. VIE I '1. [IHEU El" M'I _ |..‘.I1-t|-::IJI'-.’| .1111.- 13.2.11. I'LJI'IL'ml 1':J||c:_"_'_Lr:I‘.iIJII :11 |'-'-] |'-"'n i“ l grin” Ii “1.1111: M] _ 1-1.5!) A In M |1'-11--' | _. . _ 3.3;: 1133' M :' ut'nl' - IIHU |1-'|}|."'-.'|i'-'| | (in? ' ' Iii-13'. 13-30. 13-31. 13-32. 13-34. | |:r-'.i'-.'15- IL"3. 5 :- i:1 II .a' ILI'.:'.: i.".|.IL'I_|l|! i.||.ii"|| ¢:| .Llhtuim. .:LII'.|1 (Ella-"m- -:1'~1.-':m.-I'. '-'-"1'L'|1 'I . 'l . -.t.-u::..|-.- |:|I_'..I,||- |l“.|--' -- |"-t-' :_--' Hryr'l'm-c;:cla.::.-:"-:III':1Il'n'u:II-ttl':t.I-:'Ilt:II-:5| .Il. :.. y: |i.'||- _|| MI- I:- "m' 'l iI|---.||II|*.~|:- I'lll':|-: |1~'u|‘.t:|"||"-.- I!l'.:'l'..".|.'.-il'-. :|||:- '.-:: Ca(HC03)2, is lost by precipitation of CaCO3(s) upon heating. Permanent hardness derived from other salts, such as CaSO4, is not affected by heat. (50.0 mL)(0.010 0 mmol/mL) = 0.500 mmol Ca2+, which requires 0.500 mmol EDTA = 10.0 mL EDTA. 0.500 mmol Al3+ requires the same amount of EDTA, 10.0 mL. mmol EDTA = mmol Ni2+ + mmol 2112+ 1.250 = x + 0.250 ::> 1.000 mmol Ni2+ in 50.0 mL = 0.0200 M The formula mass of MgSO4 is 120.37. The 50.0 mL aliquot contains 50.0 mL 0.450 _ 2 (500 mL)(120.37 g/mol) — 0.373 8 mmol ofMg + Since 37.6 mL of EDTA reacts with this much Mg2+, the EDTA solution contains 0.373 9 mmol / 37.6 mL = 9.943 x 10'3 mmol/mL. The formula mass of CaCO3 is 100.09. 1.00 mL of EDTA will react with 9.943 x 10‘3 mmol of CaCOg = 0.995 mg. Total EDTA = (25.0 mL) (0.045 2 M) 1.130 mmol —- Mgz’r required = (12.4 mL) (0.012 3 M) 0.153 mmol Ni2+ + Zn2+ 0.977 mmol Zn2+ = EDTA displaced by 2,3—dimercapto—1—propanol = (29.2 mL) (0.012 3 M): 0.359 mmol 2) Ni2+ = 0.977 — 0.359 = 0.618 mmol; [Ni2+] = 0.359 mmol 50.0 mL 0.618 mmol 50.0 mL = 0.0124M [Zn2+] = = 0.007 18 M ...
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This note was uploaded on 12/10/2008 for the course CHEMISTRY CHEM 3600 taught by Professor Philipj.silva during the Fall '07 term at Uni. Tartu.

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3600_Ch13_probs - 13-1. The chelate effect is the...

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