In a separate experiment, the lab partners I. Goofed and T. Klutz treat their unknown with HCl and obtain a precipitate. They treat their precipitate with hot water and decant the supernatant. On treatment of this solid with ammonia, it dissolves. On careful acidification with HNO3 a white precipitate forms. They report that their unknown contains silver. They receive only partial credit. Why?

In a separate experiment, the lab partners I. Goofed and T. Klutz treat their unknown with HCl and obtain a precipitate. They treat their precipitate with hot water and decant the supernatant. On treatment of this solid with ammonia, it dissolves. On careful acidification with HNO3 a white precipitate forms. They report that their unknown contains silver. They receive only partial credit. Why?

Chemical Principles in the Laboratory

11th Edition

ISBN:9781305264434

Author:Emil Slowinski, Wayne C. Wolsey, Robert Rossi

Publisher:Emil Slowinski, Wayne C. Wolsey, Robert Rossi

Chapter35: Spot Tests For Some Common Anions

Section: Chapter Questions

Problem 2ASA

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A chloride unknown weighing 0.3221 g is dissolved in an acidic solution and is treated with silver nitrate. The silver chloride precipitate that forms is filtered, dried, and weighed. The weight of silver chloride obtained is 0.7332 g. Calculate the percentage of Cl- in the unknown chloride sample. Please show working clearly
2. In the preparation of the titrant, the solution must be aged for at least 24 hours in the dark. State in just 1 sentence why this step must be done.
A mixture containing only KCl and NaBr is analyzed by the Mohr method. A 0.5072-g sample is dissolved in 50 mL of water and titrated to the Ag2CrO4 end point, requiring 36.85 mL of 0.1120 M AgNO3. A blank titration requires 0.71 mL of titrant to reach the same end point. Report the %w/w KCl and NaBr in the sample.KCl = 74.551 NaBr = 102.89
A 1.000-g sample containing bromide was dissolved in sufficient water to give 100.0 mL. A 50.00 mL aliquot was measured and after acidification, silver nitrate was introduced to precipitate AgBr, which was filtered, washed, and then dissolved in an ammoniacal solution of potassium tetracyanonickelate(II): Ni(CN)42- + 2AgBr(s) → 2Ag(CN)2- + Ni2+ + 2Br- The liberated nickel ion required 11.70 mL of 0.002146 M EDTA. Calculate mmol Ni in the 50.00 mL aliquot. Calculate mmol Br- in the 50.00 mL aliquot. Calculate the percentage of NaBr (102.894) in the 1.000 g sample.
A 1.000-g sample containing bromide was dissolved in sufficient water to give 100.0 mL. A 50.00 mL aliquot was measured and after acidification, silver nitrate was introduced to precipitate AgBr, which was filtered, washed, and then dissolved in an ammoniacal solution of potassium tetracyanonickelate(II): Ni(CN)42- + 2AgBr(s) → 2Ag(CN)2- + Ni2+ + 2Br- The liberated nickel ion required 11.70 mL of 0.002146 M EDTA The other 50.00 mL remaining solution was also analyzed for its Br- content by potentiometry using a metallic electrode of the second kind. Ecell recorded in running the solution using the potentiometric set-up was Ecell = 0.0286 V. (E0Ag/AgBr = 0.095 V) g) Compute for Eind. h) Compute pBr in the 50.00 mL aliquot. i) Compute for % NaBr ( in the potentiometric technique). j) Calculate the error between the obtained % NaBr fr the EDTA titration technique and the % NaBr from the potentiometric technique.
A 1.000-g sample containing bromide was dissolved in sufficient water to give 100.0 mL. A 50.00 mL aliquot was measured and after acidification, silver nitrate was introduced to precipitate AgBr, which was filtered, washed, and then dissolved in an ammoniacal solution of potassium tetracyanonickelate(II): Ni(CN)42- + 2AgBr(s) → 2Ag(CN)2- + Ni2+ + 2Br-50.00 mL remaining solution was analyzed for its Br- content by potentiometry using a metallic electrode of the second kind. a) Write the cell notation of the potentiometric set-up with SCE as the reference electrode. b) Write the Nernst equation that describes the indicator electrode set-up. Ecell recorded in running the solution using the potentiometric set-up was Ecell = 0.0286 V. (E0Ag/AgBr = 0.095 V) c) Compute for Eind. d) Compute pBr in the 50.00 mL aliquot. e) Compute for % NaBr ( in the potentiometric technique).
Standard solution : 0.201 grams of acetylsalicylic acid was combined with 10 mL of 0.5 M NaOH, then transfered to a 100 mL flask and filled the rest of the way with water Then 0.500 mLs of the standard solution was transfered to a 10.00 mL flask and diluted to the 10 mL mark with 0.02 M of buffered iron chloride. Number of moles of NaOH = 0.005 moles Since the reaction between acetylsalicylic acid and NaOH is a 1:1 reaction, the number of moles of acetylsalicylic acid used in the reaction is also 0.005 moles. the concentration from analysis question 5: acetylsalicylic acid in the 100.00 mL volumetric flask is 0.050 M. From your plot, what is the value of εb? From the Beer- Lambert law For the aspirin sample, calculate the concentration of acetylsalicylic acid present using the value of εb that you found The concentration from analysis question 5 represents the concentration in the 10.00 mL sample that was prepared in the volumetric flask using an aliquot of the solution in the…
A mixture containing only KCl and NaBr is analyzed by the Mohr method. A 0.2125- g sample is dissolved in 25 mL of water and titrated to the Ag2CrO4 end point, requiring 25.63 mL of 0.1110 M AgNO3. A blank titration requires 1.15 mL of titrant to reach the same end point. Report the %w/w KCl and NaBr in the sample.KCl = 74.551 NaBr = 102.89
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Calculate the number of grams of oxalic acid dihydrate (M.W. = 126.1g/mol) necessary to react with 35 mL of the 0.1 M NaOH solution. Showall your calculations. Note: 35 mL is the approximate volume of NaOHsolution that needs to be used in the titration in order to obtain theprecision desired in this experiment.
The NaOH titrant in this experiment was prepared to be approximately 0.1 M and then was standardized to determine its exact concentration. What possible reasons could there be for not simply weighing the solid NaOH, dissolving to a known volume and calculating its molarity?
In this activity, you will develop an experimental procedure to solve a problem. Consider the followingscenario:You are the manager of a chemical stockroom, and find a bottle containing approximately one liter of aclear and colorless solution of unknown identity and concentration. Your only clue to its identity is thatit was found between bottles of silver fluoride and sodium fluoride, so it is likely an aqueous solution ofone of those two compounds. You will need to develop a procedure to determine the following:a) The identity of the unknown solutionb) The concentration of the unknown solutionWrite out a precise procedure, which includes all glassware, reagents, and steps. You will also need towrite the calculations that you would need to determine the concentration of the solution. Assume thatyou have access to any reagent you might need