General Chemistry
General Chemistry
7th Edition
ISBN: 9780073402758
Author: Chang, Raymond/ Goldsby
Publisher: McGraw-Hill College
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Chapter 17, Problem 17.14QP

(a)

Interpretation Introduction

Interpretation:

The pH of the given buffer solution before and after the addition of HClandNaOH have to be calculated.

Concept introduction:

  • pH is the logarithm of the reciprocal of the concentration  of H3O+  in a solution.
  •  pH is used to determine the acidity or basicity of an aqueous solution.
  • pH=-log[H3O+]
  • Buffer solution is defined as a solution that oppose changes in pH while adding little amount of either an acid or a base. In general, addition of acid or base does not affect the pH in buffer solution but if it is more than amount of conjugate base or conjugate acid, then buffer loses its buffering capacity.
  • Buffer solution is a combination of a weak acid and its conjugate base or a weak base and its conjugate acid.

To calculate: the pH of buffer solution acetic acid and sodium acetate on addition of NaOH

(a)

Expert Solution
Check Mark

Answer to Problem 17.14QP

The pH of buffer solution after addition of NaOH is 4.82

Explanation of Solution

The given concentrations of acetic acid and sodium acetate are 1.00M

The number of moles of NaOH is 0.080

ThepHofaceticacidandsodiumacetatebuffersystemisequaltopKapH=pKa=-logKaTheKavalueforacetic acidis1.8×10-5=-log(1.8×10-5)=4.74NaOHcompletelyreactswithaceticacid.hence,0.080molofOH-isaddedtobufferThereactionisasfollows,CH3COOH(aq) +OH-(aq)CH3COO-(aq)+H2O(l)Initial concentration(M): 1.00 0.0801.00Change in concentration (M):-0.080 -0.080+0.0010Equilibriumconcentration (M): 0.92 01.08Theacetic acid equilibrium table isredfined asCH3COOH(aq) H+(aq)+CH3COO-(aq)Initial concentration(M): 0.92 01.08Change in concentration (M):-x +x+xEquilibriumconcentration (M): 0.92-x 01.08+xKa=[H+][CH3COO-][CH3COOH]1.8×10-5=(x)(1.08+x)(0.92-x)xisverysmallandweneglectit,1.8×10-5=(x)(1.08)(0.92)x=[H+]=1.5×10-5pH=-log[H+]=-log(1.5×10-5)pH=4.82

When sodium hydroxide adds to the buffer solution the acetic acid reacts with it and concentration of acetic acid changes.  From the expression of Ka , the concentration of hydrogen ion can be calculated.  With the help of hydrogen ion concentration, pH of the buffer solution after addition of base can be found.  The pH value raised from 4.74to4.82 due to addition of strong base.

(b)

Interpretation Introduction

Interpretation:

The pH of the given buffer solution before and after the addition of HClandNaOH have to be calculated.

Concept introduction:

  • pH is the logarithm of the reciprocal of the concentration  of H3O+  in a solution.
  •  pH is used to determine the acidity or basicity of an aqueous solution.
  • pH=-log[H3O+]
  • Buffer solution is defined as a solution that oppose changes in pH while adding little amount of either an acid or a base. In general, addition of acid or base does not affect the pH in buffer solution but if it is more than amount of conjugate base or conjugate acid, then buffer loses its buffering capacity.
  • Buffer solution is a combination of a weak acid and its conjugate base or a weak base and its conjugate acid.

To calculate: the pH of buffer solution acetic acid and sodium acetate on addition of HCl.

(b)

Expert Solution
Check Mark

Answer to Problem 17.14QP

The pH of buffer solution after addition of HCl is 4.64

Explanation of Solution

The given concentrations of acetic acid and sodium acetate are 1.00M

The number of moles of HCl is 0.12

HClcompletelyreactswithacetate in buffer.Hence,0.12molofH+isaddedtobufferThereactionisasfollows,CH3COO-(aq) +H+(aq)CH3COOH(aq)Initial concentration(M): 1.00 0.121.00Change in concentration (M):-0.12 -0.12+0.12Equilibriumconcentration (M): 0.88 01.12Theacetic acid equilibrium table isredfined asCH3COOH(aq) H+(aq)+CH3COO-(aq)Initial concentration(M): 1.12 00.88Change in concentration (M):-x +x+xEquilibriumconcentration (M): 1.12-x 00.88+xKa=[H+][CH3COO-][CH3COOH]1.8×10-5=(x)(0.88+x)(1.12-x)xisverysmallandweneglectit,1.8×10-5=(x)(0.88)1.12x=[H+]=2.3×10-5MpH=-log[H+]=-log(2.3×10-5)pH=4.64

When hydrochloric acid adds to the buffer solution the acetate reacts with it and concentration of acetic acid changes.  From the expression of Ka, the concentration of hydrogen ion can be calculated.  With the help of hydrogen ion concentration, pH of the buffer solution after addition of acid can be found.  The pH value lowered from 4.74to4.64 due to addition of strong acid.

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Chapter 17 Solutions

General Chemistry

Ch. 17.5 - Prob. 2PECh. 17.5 - Prob. 3PECh. 17.6 - Prob. 1PECh. 17.6 - Prob. 1RCCh. 17.7 - Prob. 1PECh. 17.7 - Prob. 1RCCh. 17 - Prob. 17.1QPCh. 17 - Prob. 17.2QPCh. 17 - Prob. 17.3QPCh. 17 - 17.4 The pKbs for the bases X−, Y−, and Z− are...Ch. 17 - 17.5 Specify which of these systems can be...Ch. 17 - 17.6 Specify which of these systems can be...Ch. 17 - 17.7 The pH of a bicarbonate–carbonic acid buffer...Ch. 17 - Prob. 17.8QPCh. 17 - 17.9 Calculate the pH of the buffer system 0.15 M...Ch. 17 - 17.10 What is the pH of the buffer 0.10 M...Ch. 17 - 17.11 The pH of a sodium acetate–acetic acid...Ch. 17 - 17.12 The pH of blood plasma is 7.40. Assuming the...Ch. 17 - Prob. 17.13QPCh. 17 - Prob. 17.14QPCh. 17 - 17.16 A student wishes to prepare a buffer...Ch. 17 - Prob. 17.17QPCh. 17 - Prob. 17.18QPCh. 17 - Prob. 17.19QPCh. 17 - 17.20 A 5.00-g quantity of a diprotic acid is...Ch. 17 - Prob. 17.21QPCh. 17 - Prob. 17.22QPCh. 17 - 17.23 The diagrams shown here represent solutions...Ch. 17 - 16.38 The diagrams shown here represent solutions...Ch. 17 - 17.25 Explain how an acid-base indicator works in...Ch. 17 - 17.26 What are the criteria for choosing an...Ch. 17 - 17.27 The amount of indicator used in an acid-base...Ch. 17 - 17.28 A student carried out an acid-base titration...Ch. 17 - 17.29 Referring to Table 17.1, specify which...Ch. 17 - 17.30 The ionization constant Ka of an indicator...Ch. 17 - 17.31 Define solubility, molar solubility, and...Ch. 17 - 17.32 Why do we usually not quote the Ksp values...Ch. 17 - 17.33 Write balanced equations and solubility...Ch. 17 - Prob. 17.34QPCh. 17 - Prob. 17.35QPCh. 17 - 17.36 Silver chloride has a larger Ksp than silver...Ch. 17 - Prob. 17.38QPCh. 17 - 17.39 The molar solubility of MnCO3 is 4.2 × 10−6...Ch. 17 - Prob. 17.40QPCh. 17 - Prob. 17.41QPCh. 17 - 17.42 Using data from Table 17.2, calculate the...Ch. 17 - 17.43 What is the pH of a saturated zinc hydroxide...Ch. 17 - 17.44 The pH of a saturated solution of a metal...Ch. 17 - Prob. 17.45QPCh. 17 - 17.46 A volume of 75 mL of 0.060 M NaF is mixed...Ch. 17 - 17.47 How does a common ion affect solubility? Use...Ch. 17 - Prob. 17.48QPCh. 17 - Prob. 17.49QPCh. 17 - Prob. 17.50QPCh. 17 - Prob. 17.51QPCh. 17 - 17.52 Calculate the molar solubility of BaSO4 (a)...Ch. 17 - Prob. 17.55QPCh. 17 - Prob. 17.56QPCh. 17 - 17.57 If 2.50 g of CuSO4 are dissolved in 9.0 ×...Ch. 17 - 17.58 Calculate the concentrations of Cd2+, , and...Ch. 17 - Prob. 17.59QPCh. 17 - Prob. 17.60QPCh. 17 - Prob. 17.61QPCh. 17 - Prob. 17.62QPCh. 17 - Prob. 17.63QPCh. 17 - 16.88 In a group 1 analysis, a student adds HCl...Ch. 17 - 17.65 Both KCl and NH4Cl are white solids. Suggest...Ch. 17 - 17.66 Describe a simple test that would enable you...Ch. 17 - Prob. 17.67QPCh. 17 - Prob. 17.68QPCh. 17 - Prob. 17.69QPCh. 17 - 17.70 The pKa of the indicator methyl orange is...Ch. 17 - Prob. 17.71QPCh. 17 - Prob. 17.72QPCh. 17 - 17.73 The two curves shown here represent the...Ch. 17 - 17.74 The two curves shown here represent the...Ch. 17 - Prob. 17.75QPCh. 17 - 17.76 A solution is made by mixing exactly 500 mL...Ch. 17 - Prob. 17.77QPCh. 17 - Prob. 17.78QPCh. 17 - 17.79 For which of these reactions is the...Ch. 17 - Prob. 17.80QPCh. 17 - Prob. 17.81QPCh. 17 - Prob. 17.82QPCh. 17 - Prob. 17.83QPCh. 17 - 17.84 Find the approximate pH range suitable for...Ch. 17 - Prob. 17.85QPCh. 17 - 17.86 Which of these substances will be more...Ch. 17 - Prob. 17.87QPCh. 17 - Prob. 17.88QPCh. 17 - Prob. 17.89QPCh. 17 - Prob. 17.90QPCh. 17 - Prob. 17.91QPCh. 17 - 17.92 When a KI solution was added to a solution...Ch. 17 - Prob. 17.93QPCh. 17 - Prob. 17.94QPCh. 17 - Prob. 17.95QPCh. 17 - 17.96 Solid NaI is slowly added to a solution that...Ch. 17 - Prob. 17.97QPCh. 17 - 17.98 (a) Assuming complete dissociation and no...Ch. 17 - 17.99 Acid-base reactions usually go to...Ch. 17 - 17.100 Calculate x, the number of molecules of...Ch. 17 - Prob. 17.101QPCh. 17 - 17.102 What reagents would you employ to separate...Ch. 17 - 17.103 CaSO4 (Ksp = 2.4 × 10−5) has a larger Ksp...Ch. 17 - 17.104 How many milliliters of 1.0 M NaOH must be...Ch. 17 - Prob. 17.105QPCh. 17 - Prob. 17.106QPCh. 17 - Prob. 17.107QPCh. 17 - Prob. 17.108QPCh. 17 - Prob. 17.109QPCh. 17 - Prob. 17.111SPCh. 17 - Prob. 17.112SPCh. 17 - Prob. 17.113SPCh. 17 - Prob. 17.114SPCh. 17 - Prob. 17.115SPCh. 17 - Prob. 17.116SPCh. 17 - 17.117 The titration curve shown here represents...Ch. 17 - Prob. 17.118SP
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