A chemist titrates 190.0 mL of a 0.3300M methylamine (CH3NH2) solution with 0.2028M HBr solution at 25 °C. Calculate the pH at equivalence. The pK ofmethylamine is 3.36.Round your answer to 2 decimal places.Note for advanced students: you may assume the total volume of the solution equals the initial volume plus the volume of HBr solution added.PH=0

Given:Volume of methylamine solution = 190.0 mL (0.190 L)Concentration of methylamine: 0.3300…

Answered: A chemist titrates 190.0 mL of a…

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter15: Acid–base Equilibria

Section: Chapter Questions

Problem 55P

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Calculate the mass in grams of ammonium chloride, NH4C1, that would have to be added to 500. mL of 0.10-M NH3 solution to have a pH of 9.00.
A solution of weak base is titrated to the equivalence point with a strong acid. Which one of the following statements is most likely to be correct? a The pH of the solution at the equivalence point is 7.0. b The pH of the solution is greater than 13.0. c The pH of the solution is less than 2.0. d The pH of the solution is between 2.0 and 7.0. e The pH of the solution is between 7.0 and 13.0. The reason that best supports my choosing the answer above is a Whenever a solution is titrated with a strong acid, the solution will be very acidic. b Because the solution contains a weak base and the acid (titrant) is used up at the equivalence point, the solution will be basic. c Because the solution contains the conjugate acid of the weak base at the equivalence point, the solution will be acidic.
You have 0.10-mol samples of three acids identified simply as HX, HY, and HZ. For each acid, you make up 0.10 M solutions by adding sufficient water to each of the acid samples. When you measure the pH of these samples, you find that the pH of HX is greater than the pH of HY, which in turn is greater than the pH of HZ. a Which of the acids is the least ionized in its solution? b Which acid has the largest Kd?
Enough water is added to the buffer in Question 30 to make the total volume 5.00 L. (a) Calculate the pH of the buffer. (b) Calculate the pH of the buffer after adding 0.0250 mol of HCl to 0.376 L of the buffer. (c) Calculate the pH of the buffer after adding 0.0250 mol of KOH to 0.376 L of the buffer. (d) Compare your answers to Question 30 (a-c) with your answers to (a-c) of this problem. (e) Comment on the effect of dilution on the pH of a buffer and on its buffer capacity. Â
Methyl orange, HMO, is a common acid-base indicator. In solution it ionizes according to the equation: HMOaqH+aq+MO-aqredyellow If methyl orange is added to distilled water, the solution turns yellow. If 1 drop or two of 6 M HCl is added to the yellow solution, it turns red. If to that solution one adds a few drops of 6 M NaOH, the color reverts to yellow. a. Why does adding 6 M HCl to the yellow solution of methyl orange tend to cause the color to change to red? Note that in solution HCl exists as H+ and Cl- ions. b. Why does adding 6 M NaOH to the red solution tend to make it turn back to yellow? Note that in solution NaOH exists as Na+ and OH- ions. How does increasing OH- shift Reaction 3 in the discussion section? How would the resulting change in H+ affect the dissociation reaction of HMO?
Calculate the pH of solutions that are 0.25 M formic acid and 0.40 M sodium formate. 0.50 M benzoic acid and 0.15 M sodium benzoate.
Malic acid is a weak diprotic organic acid with Ka1 = 4.0 104 and Ka2 = 9.0 105. a Letting the symbol H2A represent malic acid, write the chemical equations that represent Ka1 and Ka2. Write the chemical equation that represents Ka1 Ka2. b Qualitatively describe the relative concentrations of H2A, HA, A2, and H3O+ in a solution that is about one molar in malic acid. c Calculate the pH of a 0.0175 M malic acid solution and the equilibrium concentration of [H2A]. d What is the A2 concentrationin in solutions b and c?
Estimate the pH that results when the following two solutions are mixed. a) 50 mL of 0.3 M CH3COOH and 50 mL of 0.4 M KOH b) 100 mL of 0.3 M CH3COOH and 50 mL of 0.4 M NaOH c) 150 mL of 0.3 M CH3COOH and 100 mL of 0.3 M Ba(OH)2 d) 200 mL of 0.3 M CH3COOH and 100 mL of 0.3 M Ba(OH)2
A solution made up of 1.0 M NH3 and 0.50 M (NH4)2SO4 has a pH of 9.26. a Write the net ionic equation that represents the reaction of this solution with a strong acid. b Write the net ionic equation that represents the reaction of this solution with a strong base. c To 100. mL of this solution, 10.0 mL of 1.00 M HCl is added. How many moles of NH3 and NH4+ are present in the reaction system before and after the addition of the HCl? What is the pH of the resulting solution? d Why did the pH change only slightly upon the addition of HCl?
Which of the acid-base indicators discussed in this chapter would be suitable for the titration of (a) HNO3 with KOH. (b) KOH with acetic acid. (c) HCl with NH3. (d) KOH with HNO2. Explain your answers.
A 0.239-g sample of unknown organic base is dissolved in water and titrated with a 0.135 M hydrochloric acid solution. After the addition of 18.35 mL of acid, a pH of 10.73 is recorded. The equivalence point is reached when a total of 39.24 mL of HCl is added. The base and acid combine in a 1:1 ratio. a What is the molar mass of the organic base? b What is the Kb value for the base? The Kb value could have been determined very easily if a pH measurement had been made after the addition of 19.62 mL of HCl. Why?
Sodium benzoate, NaC7H5O2, is used as a preservative in foods. Consider a 50.0-mL sample of 0.250 M NaC7H5O2 being titrated by 0.200 M HBr. Calculate the pH of the solution: a when no HBr has been added; b after the addition of 50.0 mL of the HBr solution; c at the equivalence point; d after the addition of 75.00 mL of the HBr solution. The Kb value for the benzoate ion is 1.6 1010.

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