REPORT SHEET EXPERIMENT Colorimetric |22 Determination of an Equilibrium Constan
ID: 545297 • Letter: R
Question
REPORT SHEET EXPERIMENT Colorimetric |22 Determination of an Equilibrium Constant in Aqueous Solution A. Preparation of the Calibration Curve Concentration of Fe(NO in 0.10 M HNO, solution Concentration of NaSCN in 0.10 M HNO, solution Flask Number Volume of NaSCN, mL Solution tnitial [SCNM Equil. (FeNcs?M Percent T B. Determination of the Equ nstantl Concentration of Fe(NO,h in 0.10 MHNO, solution Concentration of NaSCN in 0.10 MHNO, solution Test Tube Number Solation Temperature Volume of Fe(NO) Solution, mL Volume of NaSCN Solution, mL laitial [Fe J, M Initial [SCN-J,M loT 100 120 512 42 287 Copyright C 2012 Pearsoe Education,Explanation / Answer
You haven’t provided any of the concentrations; hence, I cannot calculate [Fe3+], [SCN-] or [FeSCN2+]. I shall need these values to answers questions (3)-(5).
1) A graduated cylinder is less precise than a pipette, i.e, a graduated cylinder will deliver more SCN- than a pipette. Consequently, the calculated concentrations of SCN- will be slightly higher than the actual concentrations and hence, the calculated Keq (defined as Keq = [FeSCN2+]/[Fe3+][SCN-]) will be slightly low. Consequently, the results will show variations (lower) from the actual value and the accuracy of the experiment will be low.
2) The experiment assumes that all the SCN- added is converted to FeSCN2+. If there is lower conversion of SCN- to FeSCN2+, [FeSCN2+] will be low and the equilibrium constant, Keq will be low.
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