Calculate the concentration of the unknown MnO4 sample, given the following standard additionexperiment.Step 1: A 2.00 mL aliquot of an unknown MnO4 sample was diluted to 100.0 mL and the absorbancemeasured to be 0.275.Step 2: A 2.00 mL aliquot of an unknown MnO4 sample was placed in a 100.0 mL flask. A 2.00 mLaliquot of a 100.00 ppm MnO4 standard was added to the flask and the absorbance measured to be0.6.Report your answer to one decimal place.

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Macroscale and Microscale Organic Experiments

7th Edition

ISBN:9781305577190

Author:Kenneth L. Williamson, Katherine M. Masters

Publisher:Kenneth L. Williamson, Katherine M. Masters

Chapter14: Ultraviolet Spectroscopy, Refractive Indices, And Qualitative Instrumental Organic Analysis

Section: Chapter Questions

Problem 4Q

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A compound with a molecular weight of 229.61 g/mol was dissolved in 50.0 mL of water. 1.00 mL of this solution was placed in a 10.0 mL flask and diluted to the mark. The absorbance of this diluted solution at 510 nm was 0.472 in a 1.000 cm cuvet. The molar absorptivity of the compound, at 510 nm, is 6,310 M-1 cm-1. Calculate the concentration of the compound in the initial 50.0 mL solution. A. 1.50 x 10-5 M B. 7.48 x 10-5 M C. 7.48 x 10-4 M D. 7.48 x 10-6 M
6. Blue Blue dye stock solution 0.293 M Absorbance at 630 nm 0.00265 Calibration curve y = 0.0833x A solution is prepared by diluting 2.79 mL of the blue dye stock solution to 25.00 mL. The measured absorbance for the prepared solution is listed in the data table. (a) What is the theoretical molar concentration? [Blue]theoretical x 10 |M (b) What is the experimental molar concentration? [Blue]experimental x 10 M (c) What is the percent error? Percent error (blue) = %
An unknown concentration of [FeSal]+ gave an absorbance reading of 0.301. Calculate the concentration of the solution, given that the slope of the standard curve was 1280 and the y intercept was -0.00821.
The standard curve was made by spectrophotographic analysis of equilibrated iron(III) thiocyanate solutions of known concentration. You are asked to analyze a Fe(SCN)2+ solution with an unknown concentration and an absorbance value of 0.392. The slope-intercept form of the equation of the line is y = 4538.1x +0.0077. The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe³+ concentration of the unknown solution? [Fe³+] = mol/L Absorbance Iron(III) thiocynate standard curve 1.0 V 0.5 0.0001 Fe³+ concentration (M) 0 0.0002
The nitrite in a series of standard solutions (mg/L, n = 5) are converted to azo dye and the slope of the calibration curve is 2.0 ppm. A 10.00-mL mineral water sample is treated in the same way as standards and diluted to a final volume of 100.00-mL It gives an absorbance of 0.80. The absorbance of blank solution under the same conditions is 0.10. Calculate ppm (mg/L) of NO2 (46 g/mol) and the molarity of NaNO2 (69 g/mol) in the original sample
A spectrophotometer was calibrated with a 7.236 x 10-4 M (in Cu) Cu-neocuproine solution. This calibration was carried out in a 1.00 cm cell, and yielded an absorbance of 0.2680 AU. An unknown was then analyzed in this same spectrophotometer, but using a 2.50 cm cell. If the absorbance of the unknown was 0.3700 AU, what is the Cu concentration? 4.0 M Submit Answer
A mixture is prepared by combining 10.72 mL of 2.52 x 10-3 M Fe(NO3)3 with 10.00 mL of 1.76 x 10-3 M KSCN. The solution turns red due to the formation of FeSCN2+. The absorbance is measured and, using a calibration plot, the [FeSCN2+] at equilibrium is found to be 2.25 x 10-4 M.Complete the following ICE table Fe3+ + SCN- ⇌ FeSCN2+ initial (M) (A) (B) (C) change (M) (D) (E) (F) equilibrium (M) (G) (H) (I) What is the value of Kc?
.Q1. To determine the concentrations (mol/L) of Co(NO3)2 (A) and Cr(NO3)3(B) in an unknown sample, the following representative absorbance data wereobtained.A (mol/L) B (mol/L) 510nm 575nm5×10−1 0 0.714 0.0970 6×10−2 0.298 0.757Unknown Unknown 0.671 0.330Measurements were made in 1.0 cm glass cells.i. Calculate the four molar absorptivities: ∈A(510), ∈A(575), ∈B(510) and ∈B(575).ii. Calculate the molarities of the two salts A and B in the unknown.
A 1.00 mL aliquot of a hydrogen peroxide (H2O2) solution was added to 2.00 mL of acidified Ti(IV) solution and the solution was transferred to a 1.00 mm cuvette. The absorbance of the solution against a matched reference cuvette containing Ti(IV) solution only was 0.250 at 410 nm. Determine the concentration of the H2O2 solution in mol dm–3 given that the molar absorptivity coefficient for the Ti(IV)–H2O2 complex is 770 dm3 mol–1 cm–1. Assuming the density of the H2O2 solution is 1.00 g mL–1, determine the concentration of the H2O2 solution as a %(w/w).
Suppose that you are trying to measure the concentration of SO2 in air. To do that, you followed the para-rosaniline method. The SO2 was collected in a 10-ml solution of HgCl4 2- then diluted to 25 ml after the addition of the appropriate reagents. The absorbance owas measured at 650 nm in a 2.0-cm cell, yielding a value of 0.535. A standard sample was prepared by substituting a 1.00 mL sample of a standard solution containing the equivalent of 15.00 ppm SO2 for the airsample. The absorbance of the standard is found out to be 0.191. Report the concentration of SO2 in the air in parts per million. The density of air is 1.19 g/L
The content of manganese (Mn) in steel was determined spectrophotometrically and with the use of the standard addition method. An unknown sample of Mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. When 5.00 mL of solution containing 95.5 ppm Mn was added to 50.0 mL of the unknown steel solution (digested sample), the absorbance was 0.248. Calculate the concentration, in parts-per-million (ppm), of Mn in the digested steel sample solution. NOTE: When a problem does not state diluted to a given volume, then you consider the sum of the volumes for Vf. A. 9.55 B. 20.2 C. 5.68 D. 140 E. 22.1 F. 96.7 G. 6.95
The following absorbance values for four solutions with known MnO4 concentrations were measured using a spectrophotometer: Solution 1 2 3 4 [MnO4] 0.700 x 104 M 1.00 x 104 M 2.00 x 104 M 3.50 x 104 M Absorbance 0.175 0.250 0.500 0.875 A. Using Microsoft Excel, plot a graph of Absorbance vs. Concentration of MnO4. Write the trendline linear equation from the plotted graph. B. Determine the slope of the graph and include its units. C. Determine the concentration of an unknown MnO4 sample whose absorbance is 0.780.

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