8. What volume of water must be added to 50.0 mL of HCl having pH 1.50, in order to produce a solution of HCl having pH 2.50? A. 100 mL B. 950 mL C. 25 mL D. 450 mL E. 250 mL Convert pH or pOH into [H+] or [OH-], respectively, before doing anycalculations. One cannot work with pH or pOH. Initial: [H+] = 10-pH= 10-1.50= 0.03162M Final: [H+] = 10-pH= 10-2.50= 0.003162M For dilution, one may use M1V1= M2V2. For other calculations, go through moles. M1V1= M2V20.03162M x 0.050L = 0.003162M x XL X = 0.50L = 500 mL total volume at the end. But there are 50 mL already present. Hence 450 mL of water needs to be added.
26Chem 162-2011 Hourly Exam II + Answers Chapter 15B - Applic. Of Acid & Base Equilibria (Buffers & Titrations) Acid and base equilibria calculations 19mod. 5.00 mL of a solution of NaOH having pH 13.00 is added to 495 mL of water at 25oC. What is the pH of the resultant solution? X
Chem 162-2015 Chapter 16 Tro Non-Acid-Base Equilibria 27CHEM 162-2009 HOURLY EXAM II + ANSWERS CHAPTER 15A - ACID & BASE EQUILIBRIA ACID AND BASE EQUILIBRIA CALCULATIONS 19. At 50oC, the pH of pure water is 6.63. Calculate Kwfor water at 50oC. A. 1.1 x 10-14B. 2.2 x 10-14C. 5.5 x 10-14D. 3.3 x 10-14E. 4.4 x 10-14∆+ H2O + H2O ←→H3O++ OH-Water autoionization is an endothermic reaction. At 25oC Kw= 1 x 10-14Therefore, at 50oC Kw> 1 x 10-14. pH = 6.63 [H+] = 10-6.63= 2.344 x 10-7[H2O] + [H2O] ←→[H3O+] + [OH-] Note that in pure H2O there is an equal concentration of H3O+& OH-. [H3O+] = [OH-] [H3O+][OH-] = Kw [2.344 x 10-7][ 2.344 x 10-7] = 5.50 x 10-14= Kw
Chem 162-2015 Chapter 16 Tro Non-Acid-Base Equilibria 28TABLE OF CONTENTS FOR ACID-BASE EQUILIBRIA PROBLEMSp. 30. Given initial acid concentration and Ka, find equilibrium concentrations. p. 31. Given initial acid concentration and Ka, find equilibrium concentrations (percent dissociation). p. 33. Given initial acid concentration and equilibrium concentration (% dissociation), find Ka. p. 34. Given initial acid concentration and equilibrium concentration (pH), find Ka. p. 35. Given initial base concentration and equilibriumconcentration (pH), find Kb. p. 36. Given initial base concentration and Kb, find equilibrium concentration (pH). p. 38. Given initial polyprotic acid concentration and 3 Ka’s, find all equilibrium concentrations. p. 39. Given initial diprotic acid concentration and 2 Ka’s, find all equilibrium concentrations. p. 43. Given initial basic salt concentration and Ka, find equilibrium concentration (pH). p. 44. Given initial basic salt concentration and equilibrium concentration (pH), find Ka. p. 45. Given initial acidic salt concentration and Kb, find equilibrium concentration (pH). p. 46. Given equilibrium acidic salt concentration (pH) and Kb, find initial concentration.
Chem 162-2015 Chapter 16 Tro Non-Acid-Base Equilibria 29REACTIONS OF ACIDS AND BASES WITH WATERA or CA or B or CB+ H2O←→2 Products ACID + WATERH H — A + ←→:A-+ CONJUGATE ACID + WATERH H H R—N—H + ←→R—N: H H BASE + WATERH ..