Commercial phosphate buffers are sold to maintain fish tanks at a pH of 7.Use a table of acid dissociation equilbrium constants to find all the K, values for H, PO,.AjABIUSCalculate the pka values from the Ka values. Remember that pX = -logX.pKi =pK =pk3 =What two chemical species are primarily found in solution in a phosphate buffer with a pH of 7?о Н РО, аnd PОH,PO, and HPoHPO; and PO-о Н РО, and H,РО,

Acid dissociation equilibrium constants for H3PO4 are : Ka1 = 7.2 x 10-3 Ka2 = 6.8 x 10-8 Ka3 =…

Commercial phosphate buffers are sold to maintain fish tanks at a pH of 7. Use a table of acid dissociation equilbrium constants to find all the K, values for H, PO,. <> A - -B IUSTx2 Calculate the pka values from the Ka values. Remember that pX = -logx. pKi = pK = What two chemical species are primarily found in solution in a phosphate buffer with a pH of 77 O H,PO, and PO- O H,PO, and HPO O HPO and PO O H,PO, and H, PO,

Commercial phosphate buffers are sold to maintain fish tanks at a pH of 7. Use a table of acid dissociation equilbrium constants to find all the K, values for H, PO,. <> A - -B IUSTx2 Calculate the pka values from the Ka values. Remember that pX = -logx. pKi = pK = What two chemical species are primarily found in solution in a phosphate buffer with a pH of 77 O H,PO, and PO- O H,PO, and HPO O HPO and PO O H,PO, and H, PO,

Chemistry

9th Edition

ISBN:9781133611097

Author:Steven S. Zumdahl

Publisher:Steven S. Zumdahl

Chapter15: Acid-base Equilibria

Section: Chapter Questions

Problem 8ALQ: You have a solution of the weak acid HA and add some of the salt NaA to it. What are the major...

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You have a solution of the weak acid HA and add some of the salt NaA to it. What are the major species in the solution? What do you need to know to calculate the pH of the solution, and how would you use this information? How does the pH of the solution of just the HA compare with that of the final mixture? Explain.
The common ion effect for weak acids is to significantly decrease the dissociation of the acid in water. Explain the common ion effect.
Which of the indicators in Fig. 14-8 could be used for the titrations in Exercises 61 and 63?
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?
A good buffer generally contains relatively equal concentrations of weak acid and conjugate base. If you wanted to buffer a solution at pH = 4.00 or pH = 10.00, how would you decide which weak acidconjugate base or weak baseconjugate acid pair to use? The second characteristic of a good buffer is good buffering capacity. What is the capacity of a buffer? How do the following buffers differ in capacity? How do they differ in pH? 0.01 M acetic acid/0.01 M sodium acetate 0.1 M acetic acid/0.1 M sodium acetate 1.0 M acetic acid/1.0 M sodium acetate
A friend asks the following: Consider a buffered solution made up of the weak acid HA and its salt NaA. If a strong base like NaOH is added, the HA reacts with the OH to form A. Thus the amount of acid (HA) is decreased, and the amount of base (A) is increased. Analogously, adding HCI to the buffered solution forms more of the acid (HA) by reacting with the base (A). Thus how can we claim that a buffered solution resists changes in the pH of the solution? How would you explain buffering to this friend?
A 0.250 M solution of a weak base R2NH has a pH of 10.60 at 25C. What is G for the dissociation of the weak base in water at 25C? R2NH(aq)+H2OR2NH2+(aq)+OH(aq)
Weak base B has a pKb of 6.78 and weak acid HA has a pKa of 5.12. a Which is the stronger base, B or A? b Which is the stronger acid, HA or BH+? c Consider the following reaction: B(aq)+HA(aq)BH+(aq)+A(aq) Based on the information about the acid/base strengths for the species in this reaction, is this reaction favored to proceed more to the right or more to the left? Why? d An aqueous solution is made in which the concentration of weak base B is one half the concentration of its acidic salt, BHCl, where BH+ is the conjugate weak add of B. Calculate the pH of the solution. e An aqueous solution is made in which the concentration of weak acid HA twice the concentration of the sodium salt of the weak acid, NaA. Calculate the pH of the solution. f Assume the conjugate pairs B/BH+ and HA/A are capable of being used as color-based end point indicators in acidbase titrations, where B is the base form indicator and BH is the acid form indicator, and HA is the acid form indicator and A is the base form indicator. Select the indicator pair that would be best to use in each of the following titrations: (1) Titration of a strong acid with a strong base. (i) B/BH+ (ii) HA/A (2) Titration of a weak base with a strong acid. (i) B/BH+ (ii) HA/A
A buffer is prepared in which the ratio [ H2PO4 ]/[ HPO42 ]is 3.0. (a) What is the pH of this buffer? (b) Enough strong acid is added to convert 15% of HPO42- to H2PO4-. What is the pH of the resulting solution? (c) Enough strong base is added to make the pH 7.00. What is the ratio of [H2PO4-] to [HPO42-] at this point?
Metacresol purple is an indicator that changes from yellow to purple at pH 8.2. (a) What is Ka for this indicator? (b) What is its pH range? (c) What is the color of a solution with pH 9.0 and a few drops of metacresol purple?
A diprotic acid, H2B(MM=126g/moL), is determined to be a hydrate, H2B xH2O. A 10.00-g sample of this hydrate is dissolved in enough water to make 150.0 mL of solution. Twenty-five milliliters of this solution requires 48.5 mL of 0.425 M NaOH to reach the equivalence point. What is x?
What mass of NH4Cl must be added to 0.750 L of a 0.100-M solution of NH3 to give a buffer solution with a pH of 9.26? (Him: Assume a negligible change in volume as the solid is added.)