4. A 0.5843-g sample of a plant food preparation was analyzed for its N content by the Kjeldahl method, the liberated NH3 being collected in 50.00 mL of 0.1062 M HCI. The excess acid required an 11.89 mL back-titration with 0.0925 M NaOH. Express the results of this analysis in terms of: (a) %N (FW 14.007 g/mol). (b) %urea, H2NCONH2 (FW 60.06 g/mol). (c) %(NH4)2SO4 (FW 132.141 g/mol). (d) %(NH4):PO4 (FW 149.09 g/mol).

4. A 0.5843-g sample of a plant food preparation was analyzed for its N content by the Kjeldahl method, the liberated NH3 being collected in 50.00 mL of 0.1062 M HCI. The excess acid required an 11.89 mL back-titration with 0.0925 M NaOH. Express the results of this analysis in terms of: (a) %N (FW 14.007 g/mol). (b) %urea, H2NCONH2 (FW 60.06 g/mol). (c) %(NH4)2SO4 (FW 132.141 g/mol). (d) %(NH4):PO4 (FW 149.09 g/mol).

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

Chapter15: Acid-base Equilibria

Section: Chapter Questions

Problem 128CP: Consider the titration curve in Exercise 115 for the titration of Na2Cr3 with HCl. a. If a mixture...

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Assume you dissolve 0.235 g of the weak acid benzoic acid, C6H5CO2H, in enough water to make 1.00 102 mL of solution and then titrate the solution with 0.108 M NaOH. C6H5CO2H(aq) + OH(aq) C6H5CO2(aq) + H2O() (a) What was the pH of the original benzoic add solution? (b) What are the concentrations of all of the following ions at the equivalence point: Na+, H3O+, OH, and C6H5CO2? (c) What is the pH of the solution at the equivalence point?
Consider the titration curve in Exercise 115 for the titration of Na2Cr3 with HCl. a. If a mixture of NaHCO3 and Na2CO3 was titrated, what would be the relative sizes of V1, and V2? b. If a mixture of NaOH and Na2CO3 was titrated, what would be the relative sizes of V1 and V2? c. A sample contains a mixture of NaHCO3 and Na2CO3. When this sample was titrated with 0.100 M HCl, it took 18.9 mL to reach the first stoichiometric point and an additional 36.7 mL to reach the second stoichiometric point. What is the composition in mass percent of the sample?
The titration of Na2CO3 with HCl bas the following qualitative profile: a. Identify the major species in solution at points AF. b. Calculate the pH at the halfway points to equivalence, B and D. (Hint: Refer to Exercise 113.)
Define a buffer solution. What makes up a buffer solution? How do buffers absorb added H+ or OH with little pH change? Is it necessary that the concentrations of the weak acid and the weak base in a buffered solution be equal? Explain. What is the pH of a buffer when the weak acid and conjugate base concentrations are equal? A buffer generally contains a weak acid and its weak conjugate base, or a weak base and its weak conjugate acid, in water. You can solve for the pH by setting up the equilibrium problem using the K.a reaction of the weak acid or the Kb reaction of the conjugate base. Both reactions give the same answer for the pH of the solution. Explain. A third method that can be used to solve for the pH of a buffet solution is the HendersonHasselbalch equation. What is the HendersonHasselbalch equation? What assumptions are made when using this equation?
What must be the concentration of chromate ion in order to precipitate strontium chromate, SrCrO4, from a solution that is 0.0034 M Sr2+?
A 0.5843-g sample of a plant food preparation was analyzed for its N content by the Kjeldahl method, the liberated NH3 being collected in 50.00 mL of 0.1062 M HCl. The excess acid required an 11.89 mL back-titration with 0.0925 M NaOH. Express the results of this analysis in terms of (a) %N (b) %urea, H2NCONH2 (c) %(NH4)2SO4 (d) %(NH4)3PO4
Determine the concentration (in molarity) of 25mL of Ba(OH)2 that was neutralized by 55mL of 0.150M НCI. 3.
(a) Write the net ionic equation for the reaction that occurswhen a solution of hydrochloric acid (HCl) is mixed with asolution of sodium formate (NaCHO2). (b) Calculate theequilibrium constant for this reaction. (c) Calculate theequilibrium concentrations of Na+, Cl-, H+, CHO2-, andHCHO2 when 50.0 mL of 0.15 M HCl is mixed with 50.0 mLof 0.15 M NaCHO2.
2. Using the procedure described in this module, a student determined the percent KHP in an impure sample of KHP. A 3.150-g sample of impure KHP required 41.50 mL of 0.1352M NaOH solution for titration. (a) Calculate the number of moles of NaOH required for the titration. (b) Calculate the number of moles of KHP present in the impure sample of KHP. (c) Calculate the number of grams of KHP present in the impure sample. (d) Calculate the percent of KHP in the impure sample, using Equation 8. Equation 8: percent KHP in the impure sample, % = ( mass of KHP in the sample,g/ mass of sample analyzed, g) (100%)
4. In an experiment to determine the concentration of an HCI sample of unknown concentration, 0.1 M NaOH solution was prepared in the first step. Then, 50 mL of NaOH prepared as 0.1 M and 5 drops of methylorange indicator were added to a 250 mL flask and titrated with H2C204 prepared as 0.05 M. The turning point was observed when 26 mL of H2C204 was consumed in the titration process. In the second step, 50 mL of a non-concentrated HCI solution and 5 drops of phenolphthalein solution were added to a 250 mL flask and titrated with the adjusted NaOH solution. Calculate the concentration of an HCI sample with an unknown concentration, since it is determined that 16 mL of NaOH solution was consumed after titration.
A 0.5123g sample (molar mass 204.23g/mol) of KHP was dissolved in about 25 mL of distilled water and titrated to the phenolphthalein end point with 28.75 mL of a sodium hydroxide solution. Calculate the molar concentration of the hydroxide solution.