REPORT SHEET EXPERIMENT Determination of the27 Solubility-Product Constant for a
ID: 582407 • Letter: R
Question
REPORT SHEET EXPERIMENT Determination of the27 Solubility-Product Constant for a Sparingly Soluble Salt A. Preparation of a Calibration Curve Initial [Cro, -DO z y m olume of 0.0024M K,COs 0.0024 M Kera Total voar nL Absorbance 0H Total volume 2yyll - Molar extinction coefficient for [CrO4 Average molar extinction coefficient Standard deviation (show calculations) B. Determination of the SoRrbility-Product Constant LAg l K of As Cro Absorbance 22 1.3292 -y 2. 3. 377 Copyright O 2015 Pearson Education, Inc.Explanation / Answer
A. Preparation of calibration a curve
molar extinction coefficient
1. (0.5 - 0.096)/(1.2 x 10^-4 - 2.4 x 10^-5) = 4208 M-1.cm-1
2. (0.995 - 0.5)/(2.4 x 10^-4 - 1.2 x 10^-4) = 4125 M-1.cm-1
3. (1.38 - 0.995)/(3.6 x 10^-4 - 2.4 x 10^-4) = 3208 M-1.cm-1
average molar extinction coefficient = 3847 M-1.cm-1
standrd deviation = sq,rt.[(average - individual)^2/3]
= sq.rt.[(130321 + 77284 + 408321)/3] = 453.11 M-1.cm-1
B. Determination of the solubility product constant
1. [Ag+] = 2 x 0.329/3847 = 1.71 x 10^-4 M
[C2O4^2-] = 8.55 x 10^-5 M
Ksp = [Ag+]^2.[C2O4^2-] = 2.50 x 10^-12
2. [Ag+] = 2 x 1.06/3847 = 5.51 x 10^-4 M
[C2O4^2-] = 2.75 x 10^-4 M
Ksp = 8.35 x 10^-11
3. [Ag+] = 2 x 1.1/3847 = 5.72 x 10^-4 M
[C2O4^2-] = 2.86 x 10^-4 M
Ksp = 9.36 x 10^-11
Average Ksp = 1.8 x 10^-10
standard deviation = sq.rt.[(individual-average)^2/3] = 2.2 x 10^-10
5. Qsp = [Ag+]^2/[C2O4^2-]
= (0.004 M x 0.005 L/0.010 L)^2.(0.0024 M x 0.005 L/0.010 L)
= 4.8 x 10^-9
Qsp > Ksp, so precipitation would occur
6. Ksp = 3.5 x 10^-11 (literature)
%error = (1.8 x 10^-10 - 3.5 x 10^-11) x 100/1.8 x 10^-10 = 80.55%
7. Ag2CrO4 is soluble in acidic (HNO3) mediumand it forms soluble AgNO3 and H2CrO4 in solution upon reaction
Ag2CrO4 + 2HNO3 <==> 2AgNO3 + H2CrO4
8. source of error is from incorrec titration value reading.
9. If th solution of KMnO4 was not prepared with accuracy, this would lead to error.