A 500.0-mg sample of waste ground coffee beans used as fertilizer was digested and analyzed for nitrogen using the Kjeldahl method. After digestion, the distilled ammonia was collected in 100 mL of 0.5500 M boric acid. This solution required 19.60 mL of 0.5880 M HCI for titration to the methyl red end point. Calculate the %N in the fertilizer. % N Prelim Rxn: NH3 + H3BO3 --> NH4: H2BO3 Titration Rxn: NH4: H2BO3 + HCI --> H3BO3 CI-

A 500.0-mg sample of waste ground coffee beans used as fertilizer was digested and analyzed for nitrogen using the Kjeldahl method. After digestion, the distilled ammonia was collected in 100 mL of 0.5500 M boric acid. This solution required 19.60 mL of 0.5880 M HCI for titration to the methyl red end point. Calculate the %N in the fertilizer. % N Prelim Rxn: NH3 + H3BO3 --> NH4: H2BO3 Titration Rxn: NH4: H2BO3 + HCI --> H3BO3 CI-

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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Number 1_ A 0.5707-g sample of a water-soluble fertilizer was dissolved and analysed for nitrogen using the Kjeldahl method. After digestion, the distilled ammonia was collected in 100 mL of 0.1334 M boric acid. This solution required 26.27 mL of 0.202 M HCl for titration to the methyl red end point. Calculate the % N (AW =14 g/mol) in the fertilizer.
To determine the pKa of PNP, a student needs to prepare a solution of 18.0 µM PNP in 26.0 mM MES pH 6.3, with a total volume of 950 µL. Stock solutions of 0.350 mM PNP and 100.0 mM MES pH 6.3 are available. Calculate the volume of PNP required to make the solution (in µL).
The student added universal indicator to the alkali solution at the start of the experiment. The indicator changed colour when the acid was added to the alkali. Explain how the student used this information and the pH scale to explain that this is a neutralisation reaction.
A student performed three KHP titrations in Part 1 in order to standardize their NaOH solution. They reported the following measurements: Mass of KHP + Vial Mass of 'Empty' Vial Final Burette Reading Initial Burette Reading Determination #1 Determination #2 Determination #3 14.1992 g 14.0219 g 14.0982 g 13.3149 g 13.2301 g 13.2779 g 39.21 mL 0.49 mL 35.46 mL 0.86 mL 37.42 mL 1.59 mL How many moles of NaOH did they use in their third titration? Report your answer to the correct number of significant figures and only report the numerical value (no units).
1. Determine the mass of CaCl2·2H2O (MW 147.02 g/mole) to weigh out using a four- place analytical balance to prepare 100 mL of a 0.1005 M solution of Ca2+. 2. Determine the mass of KCI to weigh out using a four-place analytical balance to prepare 100 mL of a 1 M solution of KCI (MW 74.5513 g/mole). 3. Record the solubility of calcium carbonate in water (mg/L) in your notebook. 4. Calculate the amount of calcium carbonate (mg) not in solution if a tablet is dissolved in 250 mL of water and the tablet's label claim is 600 mg calcium / tablet.
Data for titration of 15.00 mL of vinegar with approximately 1.0 M NaOH. Note you must use the exact concentration of the standard NaOH solution to calculate the moles of NaOH. Quantity Еxample Trial 1 Trial 2 Trial 3 M NaOH (exact concentration) 0.992 M 0.953 M 0.953 M 0.953 M V initial buret reading = V, 0.20 mL 1.20 mL 0.52 mL 0.15 mL V final buret reading = V, 12.90 mL 14.22 mL 13.71 mL 13.31 mL %3D Vep = VNAOH added = V; - V, 12.70 mL 13.02 mL 13.19 mL 13.16 mL Vep = VNAOH in L 0.01270 L 0.01302 L 0.01319 L 0.01316 L moles NaOH = 0.0126 mol 0.0124 mol 0.0126 mol 0.0125 mol MNAOH X VNAOH moles AA = 0.0126 mol 0.0124 mol 0.0126 mol 0.0125 mol moles NaOH V sample = V acid 0.0150 L 0.0150 L 0.0150 L 0.0150 L (15.00 mL) (15.00 mL) (15.00 mL) Actual molarity 0.840 M 0.827 M 0.840 M 0.833 M of AA Average molarity for 3 trials => of AA 0.833 M 1. Report the acetic acid (AA) concentration of vinegar in units of molarity (M). 2. Use your average AA concentration to calculate the mass…
The Kjeldahl method was used to determine the nitrogen content of a protein. A 275 µL aliquot of a 47.0 mg/mL protein solution was digested in boiling sulfuric acid. The solution was made basic and the liberated NH, was collected in 5.00 mL of 0.0512 M HCl. A volume of 7.00 mL of 0.0174 M NaOH was required to react with the excess HCl. Calculate the weight percent of nitrogen in the protein. weight percent: wt% N
A phosphate buﬀer solution (25.00 mL sample) used for a growth medium was titrated with 0.1000 M hydrochloric acid. The components of the buﬀer were sodium monohydrogen phosphate and sodium dihydrogen phosphate. The ﬁrst endpoint occurred at a volume of 10.32 mL, and the second occurred after an additional 18.62 mL was added, for a total volume of 28.94 mL. What was the total concentration of phosphate (in any form) in the buﬀer? **Please be as detailed as possible. The different volumes in this titration are a little difficult to understand** THANK you in advance.
25.00 mL of a solution containing KIO4 is treated with excess potassium iodide. IO4- + 8H+ + 7I- → 4I2 + 4H2O The resulting solution is titrated with 0.15 M sodium thiosulfate pentahydrate. The average titre was 21.76 mL. I2 + 2S2O32- → 2I- + S4O62- What is the concentration of the sodium thiosulfate solution as a percentage (w/v)
The nitrogen and protein content of a 2.8391 g sample of milk was determined using Kjeldahl analysis. After digestion, the liberated NH3 was distilled in a flask containing 25.00 mL of standard 0.250 M HCI. Titration requires 31.65 mL of standard 0.100 M N2OH to reach the desired endpoint. Calculate the weight percent of N (FW=14.01) and protein in the sample of milk. Report values in 3 SF. % N = % % Protein =
Example Questions Calculate the saponification value of a sample of castor oil from the following data: Weight of oil taken for analysis = 2.535 g Ethanolic KOH used in the hydrolysis = 1.03 M ● • Amount of KOH used in hydrolysis = 25 ml Amount of 0.514 M HCI required to neutralize excess KOH = 34.2 ml ● ● ● • Amount of 0.514 M HCI required in the titration of blank = 50.2 ml.
A student measured 20 drops of vinegar and one drop of phenolphthalein solution into a well of her well plate. After she had added 35 drops of NaOH solution to the same well, the well was full, but she had still not reached the titration endpoint. She then took a clean pipet and transferred some of the titration mixture into a second well. She rinsed the pipet with a few drops of distilled water and transferred the rinse water into the titration mixture in the second well. Then she continued adding NaOH solution to both wells until she reached the endpoint in both wells. She then recorded the total number of drops of NaOH solution added to both wells and used it to calculate the data for her vinegar titration. Briefly comment on her procedure and the accuracy of her results.