Two different analytical methods were used to determine residual chlorine in sewageeffluents. Both methods were used on the same six samples, but each sample camefrom different locations with differing amounts of contact time with the effluent. Theresults from both methods for Cl in mg/L are shown in the table below:a.SampleMethod AMethod B10.390.360.841.761.352.562343.353.924.695.357.708.33(i)(ii)What type of t-test should be used to compare the two methods and why?Do the two methods give different results? State and test the appropriatehypotheses.(iii) Does the conclusion differ whether the 90%, 95%, or 99% confidence levelsare used? Explain.Distinguish between the equivalence point and the end point of a titration.Give two (2) factors that must be considered when choosing an appropriateindicator for a neutralisation titration.b.(i)(ii)(iii) Explain the origin of the rule of thumb that indicator colour changes occur atpH = pK, ±1.Which acid would provide the sharper end point in a titration with 0.10 M NaOH0.10 M nitrous acid (K. = 7.1 × 10“) or 0.10 M iodic acid (K, = 1.7 × 10')?c.d.For the titration of 50.00 mL of 0.1000 M glycolic acid (K„(HOCH2COOH) =1.47 x 10) with 0.2000 M KOH, calculate the pH of the titrand:(i)before any KOH is added(ii)at the point of half neutralisation(iii)at the equivalence point (V.) The Al* concentration in an unknown solution was determined by back titration.50.00 mL of 0.05000 M EDTA solution was added to 50.00 mL of the unknownsolution. After 30 minutes, the excess EDTA was titrated with 0.04875 M Zn²*solution. 17.58 mL of the titrant was used.(i)a.Under what circumstances would you choose to use the back titration methodover the direct titration method in EDTA titrations?What was the molar concentration of Al³* in the unknown sample?(ii)A 0.917-g sample of canned tuna was analysed by the Kjeldahl method. 20.59 mL of0.1249 M HCI was required to titrate the ammonia that was liberated from the sample.Calculate the percentage nitrogen in the sample. (N = 14.007 amu)b.(i)(ii)State Beer-Lambert’s law and express the law mathematically.Differentiate between the real limitations and chemical deviations from Beer'sс.law.A solution containing a complex formed between Bi(III) and thiourea has a molarabsorptivity of 9.32 × 10° L cm' moľ' at 470 nm.What is the absorbance of a 5.67 x 10 M solution of the complex at 470 nmd.(i)in a 1.00-cm cell1?What is the percent transmittance of the solution described in part (i)?What is the molar concentration of the complex in a solution that has theabsorbance described in (i) when measured at 470 nm in a 2.50-cm cell?What is the energy of the radiation absorbed by the complex in kJ molr'?(ii)(iii)(iv)

a)i) Usually paired t-tests are used to compare the two methods in order to minimize the sources of…

Two different analytical methods were used to determine residual chlorine in sewage effluents. Both methods were used on the same six samples, but each sample came from different locations with differing amounts of contact time with the effluent. The results from both methods for Cl in mg/L are shown in the table below: a. Sample Method A Method B 1 0.39 0.36 1.35 2.56 2 0.84 1.76 3.35 4.69 3 4 3.92 5.35 7.70 8.33 What type of t-test should be used to compare the two methods and why? Do the two methods give different results? State and test the appropriate hypotheses. Does the conclusion differ whether the 90%, 95%, or 99% confidence levels are used? Explain. (i) (ii) (iii)

Two different analytical methods were used to determine residual chlorine in sewage effluents. Both methods were used on the same six samples, but each sample came from different locations with differing amounts of contact time with the effluent. The results from both methods for Cl in mg/L are shown in the table below: a. Sample Method A Method B 1 0.39 0.36 1.35 2.56 2 0.84 1.76 3.35 4.69 3 4 3.92 5.35 7.70 8.33 What type of t-test should be used to compare the two methods and why? Do the two methods give different results? State and test the appropriate hypotheses. Does the conclusion differ whether the 90%, 95%, or 99% confidence levels are used? Explain. (i) (ii) (iii)

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

ChapterA1: Evaluation Of Analytical Data

Section: Chapter Questions

Problem A1.23QAP

See similar textbooks

Similar questions

The accompanying data (1.00-cm cells) were obtained for the spectrophotometric titration 10.00 mL of Pd(II) with 2.44 10-4 M Nitroso R(O. W Rollins and M. M. Oldham, Anal. chem .,1971, 43, 262, DOI: 10.1021/ac60297a026). Calculate the concentration of the Pd(II) solution, given that the ligand-to-cation ratio in the colored product is 2:1
A 1.509-g samle of a Pb/Cd alloy was dissolved in acid and diluted to exactly 250.0 mL in a volumetric flask. A 50.00-mL aliquot of the diluted solution was brought to a pH of 10.0 with an HCN/NaCN buffer, which also served to mask the Cd2+; 11.56mL of the EDTA solution were needed to titrate the Pb2+. Calculate the percentage of Pb and Cd in the sample.
The concentration of ammonia in a cleaning product was determined by back titration.Firstly, 10.00 cm3 of the cleaning product was pipetted into a large conical flask,containing 250.00cm3 of 0.50 mol/l HCl to give Solution A.Following a period of reaction and shaking, 50.00cm3 of Solution A was removed anddiluted to 250 cm3 with water in a volumetric flask to give Solution B.20 cm3 samples of Solution B were titrated against 0.05 mol/l Na2CO3 solution, givingan average titre of 12.45 cm3. i) Write equations for the reactions that have taken place.ii) Determine the concentration of NH3 in the original cleaning product in mol/l,g/l, ppm, and % w/v.
A 5.00 mL tap water sample was measured out with a volumetric pipette, and added to a 25 mL Erlenmeyer flask. It was then titrated with a 0.0100 M Na2EDTA.2H2O solution, and found to take 0.635 mL of the EDTA solution to reach the blue endpoint.
The amount of iron in a meteorite was determined by a redox titration using KMnO4 as the titrant. A 0.4185 -g sample was dissolved in acid and the liberated Fe3+ quantitatively reduced to Fe2+, using a reductor column. Titrating with 0.0044 M KMnO4 requires 28.76 mL to reach the end point. Determine the %w/w Fe2O3 in the sample of meteorite. (Fe = 55.845 amu, Fe2O3 = 159.69 g/mol
b. EDTA cannot be used as a primary standard always. When can EDTA be used as a primarystandard ? Give reason why EDTA is used in complexometric titrations.
The Cr plating on a surface that measured 3.00 cm x 4.00 cm was dissolved in HCl. The pH was suitably adjusted, and 10.19 mL of 0.01441 M EDTA was then introduced. The excess reagent required a 2.91-mL back-titration with 0.007171 M Cu2+. Calculate the average weight (in mg) of Cr (51.9961 g/mol) on each square centimeter of surface.
Calculate the pZn2+ for solutions prepared by adding 0.00, 5.00, 10.00, 15.00, 20.00, 25.00 and 30.00 mL of 0.0100 M EDTA to 25.00 mL of 0.00250 M Zn2+. Assume that both the Zn2+ and EDTA are 0.0100 M in NH3 to provide a constant pH of 9.0
A 0.3045 g of CaCO3 primary standard was dissolved using concentrated HCl, evaporated to incipient dryness, and quantitatively transferred to a 250 mL volumetric flask and diluted to mark. A 10 mL of aliquot was then transferred to an Erlenmeyer flask, together with 5mL buffer and 5 drops of EBT indicator, and was used to standardize the EDTA titrant. The solution turned blue after the addition of 24.10 mL of EDTA. A blank correction was made and was determined to be 0.4 mL. [Analysis] A 30 mL unknown water sample was treated with 37.6 mL of EDTA. A blank correction was made and was determined to be 0.4 mL. What is the concentration of Ca2+ (40.0780 g/mol) in ppm?
A 0.3045 g of CaCO3 primary standard was dissolved using concentrated HCl, evaporated to incipient dryness and quantitatively transferred to a 250 mL volumetric flask, and diluted to mark. A 10 mL of aliquot was then transferred to an Erlenmeyer flask, together with 5mL buffer and 5 drops of EBT indicator, and was used to standardize the EDTA titrant. The solution turned blue after the addition of 24.10 mL of EDTA. A blank correction was performed and was determined to be 0.4 mL. What is the concentration of EDTA obtained (MW CaCO3 = 100.0869 g/mol)?
To find the copper content in 50 mL of sample, a titration is carried out with 0.01 M AEDT. A selective Cu electrode is used to determine the end point of the titration. Three assessments are performed that use 12.5 mL, 12.3 mL; 12.4 mL of 0.01 M EDTA.a) Indicate the equipment and material necessary to carry out the potentiometric assessment.b) Indicate the reagent that must be added to the sample for the correct performance of the titration. explain the reason.c) Calculate the Cu concentration of the sample (in mg/L).Data: atomic weight Cu = 63.5
Traces of aniline can be determined by reaction with an excess of electrolytically generated Br2: C6H5NH2 + 3Br2 =====è C6H2Br3NH2 + 3H+ + 3Br- The polarity of the working electrode is then reversed, and the excess bromine is determined by a coulometric titration involving the generation of Cu(I): Br2 + 2Cu+ ===è 2Br- + 2Cu2+ Suitbale quantities of KBr and copper (II) sulfate were added to a 25.0 ml sample containing aniline (C6H5NH2). Calculate the mass in micrograms of C6H5NH2 in the sample from the accompanying data. Working electrode Functioning as Generation Time (min) with a constant current of 1.00 mA Anode 3.76 cathode 0.270