Calculate the pH of a buffer solution prepared from1.55\times 10^-5 mol of phosphoric acid,2.50\times 10^-5 mol of KH2PO4, and enough waterto make 0.500 L of solution.-H3PO4 H2PO4 + H+ pKa1H2PO4= 2.14,=HPO4 2+ H+ pKa2 = 7.20,HPO4 2PO4 3- + H+ pKa3 = 12.37

Step 1: A solution that contains a weak acid and its conjugate base is an acidic buffer solution. To…

Answered: Calculate the pH of a buffer solution…

Chemistry: Principles and Practice

3rd Edition

ISBN:9780534420123

Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Publisher:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Chapter16: Reactions Between Acids And Bases

Section: Chapter Questions

Problem 16.89QE

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Determine the dominant acid-base equilibrium that results when each of the following pairs of solutions is mixed. Indicate the equilibrium by writing 1 for a strong acid, 3 for a weak acid, 4 for an acidic buffer, 7 for a neutral solution, 10 for a basic buffer, 11 for a weak base, and 13 for a strong base. (a) 10.0 mL of 0.15 M NaOH + 15.0 mL of 0.10 M HNO3 (b) 25.0 mL of 0.10 M HCl + 10.0 mL of 0.25 M NH3 (c) 50.0 mL of 0.050 M NaOH + 50.0 mL of 0.10 M NH3 (d) 50.0 mL of 0.10 M NH3 + 50.0 mL of 0.05 M HCl
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?
What is an acidbase indicator? Define the equivalence (stoichiometric) point and the end point of a titration. Why should you choose an indicator so that the two points coincide? Do the pH values of the two points have to be within 0.01 pH unit of each other? Explain.
Ka for formic acid is 1.7 104 at 25C. A buffer is made by mixing 529 mL of 0.465 M formic acid, HCHO2, and 494 mL of 0.524 M sodium formate, NaCHO2. Calculate the pH of this solution at 25C after 110 mL of 0.152 M HCl has been added to this buffer.
Water is accidentally added to 350.00 mL of a stock solution of 6.00 M HCI. A 75.00-mL sample of the diluted solution is titrated to pH 7.00 with 78.8 mL of 4.85 M NaOH. How much water was accidentally added? (Assume that volumes are additive.)
Sketch a titration curve for the titration of potassium hydroxide with HCl, both 0.100 M. Identify three regions in which a particular chemical species or system dominates the acid-base equilibria.
8-71 Explain why you do not need to know the chemical formula of a buffer compound to use it.
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?
Ammonia gas is bubbled into 275 mL of water to make an aqueous solution of ammonia. To prepare a buffer with a pH of 9.56, 15.0 g of NH4Cl are added. How many liters of NH3; at 25C and 0.981 atm should be used to prepare the buffer? Assume no volume changes and ignore the vapor pressure of water.
Calculate the mass of sodium acetate, NaCH3COO, you should add to 500. mL of a 0.150-M solution of acetic acid, CH3COOH, to buffer a solution at a pH of 4.57.
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 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?

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Calculate the pH of a buffer solution prepared from 1.55\times 10^-5 mol of phosphoric acid, 2.50\times 10^-5 mol of KH2PO4, and enough water to make 0.500 L of solution. - H3PO4 H2PO4 + H+ pKa1 H2PO4 = 2.14, =HPO4 2+ H+ pKa2 = 7.20, HPO4 2PO4 3- + H+ pKa3 = 12.37