Consider two weak acids, with pKa values of 1.8 and 4.5. Calculate the fraction binding of each for thecase when pH = pKa, and the fraction binding when pH = 6.0. When we say the pH = pKa at the midpoint of a titration curve, we are assuming slight dissociation ofweak acids. What does your answer to question 1 say about the validity of this assumption?

Consider two weak acids, with pKa values of 1.8 and 4.5. Calculate the fraction binding of each for thecase when pH = pKa, and the fraction binding when pH = 6.0. When we say the pH = pKa at the midpoint of a titration curve, we are assuming slight dissociation ofweak acids. What does your answer to question 1 say about the validity of this assumption?

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter8: Polyfunctional Acids And Bases

Section: Chapter Questions

Problem 3P

See similar textbooks

Similar questions

The following is list of weak acids and their pką values weak acid pKa benzoic acid 4.20 hydrogen citrate 6.40 hydrocyanic acid 9.31 hydrogen phosphate 12.38 Which would be the best buffer to use at pH 7 ? For benzoic acid, a 50:50 mixture of benzoic acid and its conjugate base, the benzoate ion, would have pH = The buffering capacity of a benzoic acid:benzoate buffer would be at pH = 7 A. 4.20 B. 6.40 C. 9.31 D. 12.38 E. benzoic acid F. hydrogen citrate G. hydrocyanic acid H. hydrogen phosphate I. good J. bad
Which of these compounds would be the best buffer at pH 5.0: formic acid (pKa = 3.8), acetic acid (pKa = 4.76), or ethylamine (pKa = 9.0)? Briefly justify your answer.
In a similar experiment to the one you have performed a student is measuring the equilibrium for an organic acid that is soluble in water and in cyclohexane, a nonpolar organic solvent. When shaken with the solution of water and cyclohexane, it distributes between the organic and aqueous phase. The two phases are separated and titrated with 0.120 M NaOH. Calculate the equilibrium constant for an acid where the titration of the aqueous phase requires 9.92 mL of the base and the organic phase requires 1.51 mL of the base.
Given the titration curves below, answer the following questions. 14 12 10 6. 4 Volume of strong base (mL) Hd
Leucine has two dissociable protons: one with a pKa of 2.3, the other with a pKa of 9.7. Sketch a properly labeled titration curve for leucine titrated with NaOH; indicate where the pH = pI and the region(s) in which buffering occurs. Please be as precise as possible in the way you draw your graph (axis, units, position of data points, etc....).
The data below show how the pKa of Tris (Tris(hydroxymethyl)aminomethane) (a common buffer used in biological labs) changes with temperature. If the trend in these data holds true at higher temperatures (up to, say, 90 °C), then what is the pKa of this buffer when the temperature is 72 °C? Report your answer to the nearest hundredth. Temp. (°C) pka 25 35 45 55 8.06 7.78 7.50 7.22
Why is ethylene-di-amine tetra-acetic acid (EDTA) work as a base in complexometric titration? answer at your own words and answer should be to the point, not any irrelevant words
I need help understanding why the ratio of Acetate:Acetic acid = 3.5:1 and why the total amount would be 4.5. The question was calculate the ratio of the concentrations of acetate and acetic acid required in a buffer system of pH 5.30. The pka of acetic is 4.76. Where is the 1 coming from in the ratio 3.5:1 The second part of the question said what if the question aked for the molar concentration of acetate and acetic acid in this buffer given that the over all buffer was 0.5 M. Why is the total amount 4.5?
Three-point calibration was not performed on the pH meter prior to titration. Is there a positive error, negative error, no effect, or error could not be determined In terms of the Computed pKa of the unknown weak acid?
Match each circumstance to an outcome. (Two circumstances may have the same outcome.) The pH buffers used to calibrate the pH meter were each 0.5 pH units high (4.5 and 7.5 rather than 4.0 and 7.0 respectively). You decided to take the pH after each addition of 5.0 mL of NaOH rather than after every 0.5 mL during the neutralization of your acid sample. 1. pKa would be unchanged. 2. pka would be too high. You refilled your buret between titrations of your unknown acid. Instead of 3. pKa would be too low. using 0.1 M NaOH as you did for the first titration, you used 0.2 M NaOH. While using the Half Volume method, your solution was dark pink (you overshot the endpoint) and you added the unreacted acid to this solution.
If the stoichiometric concentrations of Ac- and HAc in Solution C were known to be 0.02816 M and 0.07104 M, respectively after mixing, then calculate the theoretical pH of Solution C after mixing. Use the literature value for the pKa of acetic acid, which is 4.77. Report your final answer to 2 decimal places. Solution C contains 20mL of buffer and 5mL of HCl.
Calculate the pH at each of the following points for the titration of 100 mL of 0. 6 M dl-Histidine with the following volumes of 1.20 M sodium hydroxide. H3His + H* + H,His Ka1 = 3.98x103 H2His + H* + HHİS2- Ka2 = 9.12x10:7 HHİS2. + H* + His3. Ka3 = 4.67x1o-10 Vol. of NaOH Calculated pH O mL 30 mL 50 mL