Don't used hand raiting an LearningSuppose a biochemist has 10 mL of a 1.0 M solution of a compound with two ionizable groups at a pH of 7.90. She adds10.0 mL of 1.0 M HCI, which changes the pH to 3.00. The pKa value of one of the groups is pK₁ = 3.80 and it is known thatpK2 is between 7 and 10. What is the exact value of pK2?

First, let's understand what we know:Initially, there's 10 mL of a 1.0 M solution with two ionizable…

Answered: an Learning Suppose a biochemist has 10…

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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Amino acids are an important group of compounds. At low pH, both the carboxylic acid group (CO2H) and the amine group (NHR) are protonated. However, as the pH of the solution increases (say, by adding base), the carboxylic acid proton is removed, usually at a pH between 2 and 3. In a middle range of pHs, therefore, the amine group is protonated, but the carboxylic acid group has lost the proton. (This is called a zwitterion.) At more basic pH values, the amine proton is dissociated. What is the pH of a 0.20 M solution of alanine hydrochloride, [NH3CHCH3CO2H]Cl?
Cacodylic acid (dimethylarsinic acid, HAsO2(CH3)2) is a common buffer used in biology to prepare and fix biological samples. It has a pKa value of 6.3.Calculate the pH of a buffer solution prepared by mixing 10.0 mL of 0.100 M NaOH with 20.0 mL of 0.150 M cacodylic acid.Express your answer to two decimal places. pH = (not 6.60)
You want to prepare 100.0 mL of a buffer solution with a pH of 4.95 by mixing appropriate volumes of 0.10 M CH3CO2H and 0.10 M NaCH3CO2. How many milliliters (mL) of the acetic acid and sodium acetate solution are needed? (CH3CO2H has Ka = 1.8 x 10–5) (A) 75.0 mL of 0.10 M CH3CO2H + 25.0 mL of 0.10 M NaCH3CO2; (B) 62.0 mL of 0.10 M CH3CO2H + 38.0 mL of 0.10 M NaCH3CO2; (C) 38.0 mL of 0.10 M CH3CO2H + 62.0 mL of 0.10 M NaCH3CO2; (D) 25.0 mL of 0.10 M CH3CO2H + 75.0 mL of 0.10 M NaCH3CO2;
The titration of CH3COOH (Ka = 1.76x10-4; pKa = 3.754; Kb = 5.68x10-11) with NaOH is an example of a weak acid/strong base titration. A 40 mL aliquot of a 0.060 M solution of HCOOH is titrated by 0.060 M KOH. What is the pH of the solution at each of the following points: a) initially b) after 1 mL of base has been added c) after 20 mL of base has been added d) at the equivalence point e) after 45 mL of bases has been added
Which of the following acids (listed with pKa values) and their conjugate base should be used to form a buffer with a pH of 8.10? HC7H5O2, pKa = 4.19 HF, pKa = 3.46 HClO, pKa = 7.54 H2SO3, pKa = 1.77 HClO2, pKa = 1.96
Strong base is dissolved in 665 mL of 0.600 M weak acid (K₁ = 4.09 × 10−5) to make a buffer with a pH of 3.96. Assume that the volume remains constant when the base is added. HA(aq) + OH(aq) H,O(l) + A-(aq) Calculate the pKa value of the acid, and determine the number of moles of acid initially present. pK₂ = initial amount: When the reaction is complete, what is the concentration ratio of conjugate base to acid? [A-] [HA] = How many moles of strong base were initially added? amount added: mol HA mol OH-
In the titration of 60.0 mL of 1.0 M methylamine, CH3NH₂ (K₁ = 4.4 x 10-4), with 0.50 M HCI, calculate the pH under the following conditions. (a) after 0.00 mL of 0.50 M HCI has been added 4.0 (b) after 20.0 mL of 0.50 M HCI has been added 4.0✔ (c) after 60.0 mL of 0.50 M HCI has been added 4.0✔ (d) at the stoichiometric point 4.0✔ (e) after 200.00 mL of 0.50 M HCI has been added 4.0
For 270.0 mL of a buffer solution that is 0.245 M in HCHO2 and 0.290 M in KCHO2, calculate the initial pH and the final pH after adding 0.031 mol of NaOH. (Ka (HCHO2) = 1.8 × 10-4.) Express your answers to two decimal places. Enter your answers numerically separated by a comma. pHinitial, pHfinal = ΜΕ ΑΣΦ Submit Previous Answers Request Answer ?
A solution is made by mixing 50.0 mL of a stock solution of 2.0 M K2HPO4 and 25.0 mL of a stock solution of 2.0 M KH2PO4. The solution is diluted to a final volume of 200.0 mL. What is the pH of the resulting solution given that the pKa of H2PO4- is 6.82?
9) The dissociation equilibrium constants for the protonated form of alanine (a diprotic amino acid, H₂X+) are Kal = 4.6 × 10-3 and Ka2=2.0 × 10-10. What is the pH of 50.00 mL of a 0.050 M solution of alanine after 37.50 mL of 0.100 M NaOH has been added? Para Ofind moles
Which is the best solution to buffer at pH = 10.50? (A) A buffer solution containing 0.25 M H2CO3 and 0.45 M Na2CO3; (Ka (H2CO3) = 4.3 x 10–7) (B) A buffer solution containing 0.25 M NaHCO3 and 0.45 M Na2CO3; (Ka (HCO3–) = 5.6 x 10–11) (C) A buffer solution containing 0.12 M NaHCO3 and 0.22 M Na2CO3; (Ka (HCO3–) = 5.6 x 10–11) (D) A buffer solution containing 0.12 M NH4Cl and 2.2 M NH3; (Ka (NH4+) = 5.6 x 10–10)
Cacodylic acid (dimethylarsinic acid, HAsO2(CH3)2) is a common buffer used in biology to prepare and fix biological samples. It has a pKa value of 6.3.Calculate the pH of a buffer solution prepared by mixing 10.0 mL of 0.100 M NaOH with 20.0 mL of 0.150 M cacodylic acid.Express your answer to two decimal places. ------------------------- Write the ions present in solution of RbHCO3.Express your answers as chemical formulas separated by a comma (NO spaces!).Identify all of the phases in your answer (e.g. NO3-(aq),Cu2+(aq) )

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