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Lab 7 Photometric Determination of an Equilibrium Constant

# Lab 7 Photometric Determination of an Equilibrium Constant...

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Unformatted text preview: Section {y 6 - EXPERIMENT 7 PHOTOMETRIC DETERMINATION OF AN EQUILIBRIUM CONSTANT PRE-LABORATORY QUESTIONS : The following preparatory questions should be answered before coming to lab. They E E are intended to introduce you to several ideas that are important to aspects of the : ; experiment. You must turn in your work to your instructor before you will be 1 : allowed to begin the experiment. I 1. Write an equilibrium expression, Keq for each of the following reversible reactions: a) 2 KNO3 (s) ¢—> 2 KNOz (s) + 02 (g) [5940331 3” fﬂe {f 5:35: T b) PC15 (g) H PC13 (1) + C12 (g) ri I ~22 - w . WW, 2. Calculate the equilibrium constant, Keq, for the system Pb2(CO3)3 (s) —-> 2 Pb3+ (aq) + 3 C032' (aq) if the equilibrium concentration of Pb3+ = 4.6 x 10'5 M and C032‘ = 6.9 x 10'5 M. Cheml 5 ISﬁAcademic Year 2010/201 l Section 0 POST LABORATORY QUESTIONS 1. In the space below enter the concentrations of F e3 + and SCN' in test tube ‘B’, Fe3+ = “2525:; it?” SCN==€§AQ'€%A Absorbance = ; My a) When a few drops of F 63+ are added to test tube ‘B’ the absorbance of the solution does not change signiﬁcantly. Give a brief explanation of your observation. we" ﬁt; A» 5%.. a... Z 36/»? .2 3’ 5'3 i ‘ ‘3‘“ ~ M ‘ i ;z .11 .j i‘ - h” Mi b) When a few drops of SCN' are added to test tube ‘B’ the absorbance of the solution does change. Give a brief explanation of your observation. A f W Vi M- ‘ i . , f . a 2 5! ‘ "3+ :i‘ ,1 " ~ ‘ "' {3‘4 7‘38 x r A! , w: , , g . a: 19* at! “A a,“ r g {I} in. its, a ,+ 3.5;: Afﬁy: “f ‘y 4m}? ' ‘1 1 ﬂaﬁ"f"'£ 131/? 5 a a «Q». 2. If, while preparing solutions A in Part One, the solution in the pipet turns brownish red, explain what has happened and why it is necessary to repeat the preparation of that test tube. w A i Jr: 4, "a -é- { JG: 9 ,-' r r Q 4,} Maggi x; ﬁre,CN ,. w w ~ﬁae~~ «»- s 9 'j 7“ 7% b 1 ("w , wig \$2., “ {Ms «A? we“? erg} Chen—115 15A-Academic Year 2010/2011 3 Section é RESULTS PART ONE: CALIBRATION LINE PREPARATION [Fey] [SCN'] [138*] after [SCN‘] [FeSCN *1 before before mixing after at S a f 1 » mixing mixing mixing eqyilibrium wo'ﬁm l./oom am am Zomc WW 3 MTV/i" / Sample calculation of initial reactant concentrations at the time of mixing for solution B. M i, h, f. m We” 3: H “ r; “3+1 g; \ ﬂ r z i’ “5/ m z owrb ;n-~~> {/1 €— ,\oO ’1' / 2? Saw, ,,_“_3; g .3?" M n ,. (pZ°QW"\lL.OI:E§> ﬂ” " 1 r , 00 i i e ":2 Em‘é /i'/ W Li .. R *‘t"\ >1; {4(( Lu g ‘ V Q2 KID ‘ 0 If,» i V 24) P x _ M ', {1:02 {.3 ’14 fax} :ﬂsggg .1 )4 ’5 Chem] 5 1 S—Academic Year 2010/20] 1 7—9 Section 5 [SCN'] [FeSCN2+] before before mixing [Fe +] after [SCN'] mixing after at, mixing equilibrium 6x/0p7y‘4 €I7Y/0'Vﬂ4 2,“?!K/0-‘4 /;0/ 2V0-” lac/mo”? Sample calculation of initial reactant concentrations at the time of mixing for solution G. . , - ,x / #4 g// H”! or, .35: Fe“. /v HS}? 2% ’9‘“ LP? J ,7 V51 ‘J 0”” c’ " m“ 22'; SCN' : Cheml 5 lS—v-Academic Year 2010/2011 1 ...
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Lab 7 Photometric Determination of an Equilibrium Constant...

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