28. Answer the following questions to find the mass (g) of dipotassium phthalate must be added to 250 mL of 0.0250 M phthalic acid to give a buffer of pH 5.75? MW K2P = 242.32 g/mol Ka2 = [H30^+] [P^-] / [HP^-] = 3.91 x 10^-6 What is the amount of P^2- needed in the buffer? 164.92 mmol 82.46 mmol 53.88 mmol 27.49 mmol

28. Answer the following questions to find the mass (g) of dipotassium phthalate must be added to 250 mL of 0.0250 M phthalic acid to give a buffer of pH 5.75? MW K2P = 242.32 g/mol Ka2 = [H30^+] [P^-] / [HP^-] = 3.91 x 10^-6 What is the amount of P^2- needed in the buffer? 164.92 mmol 82.46 mmol 53.88 mmol 27.49 mmol

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 121CP: A buffer is made using 45.0 mL of 0.750 M HC3H5O2 (Ka = 1.3 105) and 55.0 mL of 0.700 M NaC3H5O2....

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A buffer is made using 45.0 mL of 0.750 M HC3H5O2 (Ka = 1.3 105) and 55.0 mL of 0.700 M NaC3H5O2. What volume of 0.10 M NaOH must be added to change the pH of the original buffer solution by 2.5%?
A buffer solution with it pH of 12.00 consists of Na3PO4 and Na2HPO4. The volume of solution is 200.0 mL. (a) Which component of the buffer is present in a larger amount? (b) If the concentration of Na3PO4 is 0.400 M, what mass of Na2HPO4 is present? (c) Which component of the buffer must be added to change the pH to 12.25? What mass of that component is required?
Potassium hydrogen phthalate, known as KHP (molar mass = 204.22 g/mol), can be obtained in high purity and is used to determine the concentration of solutions of strong bases by the reaction HP(aq)+OH(aq)H2O(l)+P2(aq) If a typical titration experiment begins with approximately 0.5 g KHP and has a final volume of about 100 mL, what is an appropriate indicator to use? The pKa for HP is 5.51.
Fifty cm3 of 1.000 M nitrous acid is titrated with 0.850 M NaOH. What is the pH of the solution (a) before any NaOH is added? (b) at half-neutralization? (c) at the equivalence point? (d) when 0.10 mL less than the volume of NaOH to reach the equivalence point is added? (e) when 0.10 mL more than the volume of NaOH to reach the equivalence point is added? (f) Use your data to construct a plot similar to that shown in Figure 14.10 (pH versus volume NaOH added).
Consider 0.0010-M solutions of these sparingly soluble solutes in equilibrium with their ions. Predict the effect on each equilibrium if a saturated solution of sodium iodide were added. Explain your prediction in each case. AgI(s) ⇌ Ag+(aq) + I−(aq) PbI2(s) ⇌ Pb2+(aq) + 2 I−(aq)
Consider the titration of 100.0 mL of 0.100 M H2NNH2 (Kb = 3.0 106) by 0.200 M HNO3. Calculate the pH of the resulting solution after the following volumes of HNO3 have been added. a. 0.0 mL b. 20.0 mL c. 25.0 mL d. 40.0 mL e. 50.0 mL f. 100.0 mL
A buffer solution is composed of 1.360 g of KH2PO4 and 5.677 g of Na2HPO4. (a) What is the pH of the buffer solution? (b) What mass of KH2PO4 must be added to decrease the buffer solution pH by 0.50 unit from the value calculated in part (a)?
What is the pH change when 20.0 mL of 0.100 M NaOH is added to 80.0 mL of a buffer solution consisting of 0.169 M NH3 and 0.183 M NH4Cl?
Two acids, each approximately 0.01 M in concentration, are titrated separately with a strong base. The adds show the following pH values at the equivalence point: HA, pH = 9.5, and HB, pH = 8.5. (a) Which is the stronger acid, HA or HB? (b) Which of the conjugate bases, A or B, is the stronger base?
Which of these buffers involving a weak acid HA has the greater resistance to change in pH? Explain your answer. (i) [HA] =0.100 M = [A] (ii) [HA] = 0.300 M = [A]
A buffer is made up of 0.300 L each of 0.500 M KH2PO4 and 0.317 M K2HPO4. Assuming that volumes are additive, calculate (a) the pH of the buffer. (b) the pH of the buffer after the addition of 0.0500 mol of HCl to 0.600 L of buffer. (c) the pH of the buffer after the addition of 0.0500 mol of NaOH to 0.600 L of buffer.
You dissolve 0.425 g of NaOH in 2.00 L of a buffer solution that has [H2PO4| = [HPO42] = 0.132 M. What is the pH of the solution before adding NaOH? After adding NaOH?