Calculate the pH of the following buffers (give your answers with 2 decimal places) The pH of a buffer solution that is 0.50 M in HCIO and 0.40 M in NaCIO (Ka of HCIO = 3.5E-8) is The pH of a buffer solution that is 0.25 M in HF and 0.50 M in NaF (Ka of HF = 6.4E-4) is The pH of a buffer solution that is 0.25 M in NH3 and 0.50 M in NH4CI (Kb of NH3 = 1.8E-5) is The pH of a buffer solution that is 0.10 M in CH3NH2 and 0.10 M in CH3NH3CI (Kb of CH3NH2 = 4.4E-4) is

Calculate the pH of the following buffers (give your answers with 2 decimal places) The pH of a buffer solution that is 0.50 M in HCIO and 0.40 M in NaCIO (Ka of HCIO = 3.5E-8) is The pH of a buffer solution that is 0.25 M in HF and 0.50 M in NaF (Ka of HF = 6.4E-4) is The pH of a buffer solution that is 0.25 M in NH3 and 0.50 M in NH4CI (Kb of NH3 = 1.8E-5) is The pH of a buffer solution that is 0.10 M in CH3NH2 and 0.10 M in CH3NH3CI (Kb of CH3NH2 = 4.4E-4) is

Introductory Chemistry: A Foundation

9th Edition

ISBN:9781337399425

Author:Steven S. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Donald J. DeCoste

Chapter16: Acids And Bases

Section: Chapter Questions

Problem 10ALQ

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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?
8-60 How is the buffer capacity affected by the ratio of the conjugate base to the conjugate acid?
8-55 We commonly refer to a buffer as consisting of approximately equal molar amounts of a weak acid and its conjugate base—for example, CH3COOH and CH3COO-. Is it also possible to have a buffer consisting of approximately equal molar amounts of a weak base and its conjugate acid? Explain.
8-93 Do a 1.0 M CH3COOH solution and a 1.0 M HCI solution require the same amount of 1.0 M NaOH to hit a titration end point? Explain.
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?
8-101 Suppose you have an aqueous solution prepared by dissolving 0.050 mol of NaH2PO4 in 1 L of water. This solution is not a buffer, but suppose you want to make it into one. How many moles of solid Na2HPO4 must you add to this aqueous solution to make it into: (a) A buffer of pH 7.21 (b) A buffer of pH 6.21 (c) A buffer of pH 8.21
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.
8-71 Explain why you do not need to know the chemical formula of a buffer compound to use it.
8-54 Write equations to show what happens when, to a buffer solution containing equimolar amounts of HPO42- and H2PO4-, we add (a) H3O+ (b) OH-
8-115 When a solution prepared by dissolving 0.125 g of an unknown diprotic acid in 25.0 mL of water is titrated with 0.200 M NaOH, 30.0 ml, of the NaOH solution is needed to neutralize the acid. Determine the molarity of the acid solution. What is the molar mass of the unknown diprotic acid?
8-51 What is the end point of a titration?
Each symbol in the box below represents a mole of a component in one liter of a buffer solution; represents the anion (X-), = the weak acid (HX), = H+, and =OH. Water molecules and the few H+ and OH- ions from the dissociation of HX and X- are not shown. The box contains 10 mol of a weak acid, , in a liter of solution. Show what happens upon (a) the addition of 2 mol of OH- (2 ). (b) the addition of 5 mol of OH- (5 ). (c) the addition of 10 mol of OH- (10 ). (d) the addition of 12 mol of OH- (12 ). Which addition (a)-(d) represents neutralization halfway to the equivalence point?