General Chemistry
General Chemistry
7th Edition
ISBN: 9780073402758
Author: Chang, Raymond/ Goldsby
Publisher: McGraw-Hill College
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Chapter 17, Problem 17.68QP

(a)

Interpretation Introduction

Interpretation:

The pH of titration HClVsCH3NH2 has to be calculated.

Concept introduction:

  • Titration is used to find out the strength of an unknown solution from a concentration of known solution.  A standard solution whose concentration is known, is dropped slowly to an unknown solution and wait for the chemical reaction finish.
  • The point at which amount of standard solution and analyte becomes equal and neutralisation happens in titration is called equivalence point.
  • pH is the logarithm of the reciprocal of the concentration  of H3O+  in a solution.
  •  pH is used to determine the acidity of an aqueous solution.

To calculate: pH of 25.0 mL of 0.100MHCl Vs10.0 mL of 0.100 MCH3NH2

(a)

Expert Solution
Check Mark

Answer to Problem 17.68QP

pH = 1.37

Explanation of Solution

The given data is recorded as such.

0.100 M HCl0.100 M CH3NH2

  HCl(aq) +CH3NH2(aq)CH3NH3Cl(aq)Initialconcentration (M):   2.50 ×103   1.00 ×103               0Changeinconcentration (M):  1.00 ×103    1.00 ×103  +1.00 ×103Final concentration(M):  1.50 ×1030           1.00 ×103

  [H+]=1.50×103mol0.0350LpH =-log[H+] = -log[0.0429] = 1.37

The concentration of hydrogen ion is calculated from equilibrium table.  Using the concentration of hydrogen ion, the pH is determined by taking negative logarithm of concentration of hydrogen ion.

(b)

Interpretation Introduction

Interpretation:

The pH of titration HClVsCH3NH2 has to be calculated.

Concept introduction:

  • Titration is used to find out the strength of an unknown solution from a concentration of known solution.  A standard solution whose concentration is known, is dropped slowly to an unknown solution and wait for the chemical reaction finish.
  • The point at which amount of standard solution and analyte becomes equal and neutralisation happens in titration is called equivalence point.
  • pH is the logarithm of the reciprocal of the concentration  of H3O+  in a solution.
  •  pH is used to determine the acidity of an aqueous solution.

To calculate: pH of 25.0 mL of 0.100MHCl Vs25.0 mL of 0.100 MCH3NH2

(b)

Expert Solution
Check Mark

Answer to Problem 17.68QP

  pH = 5.97

Explanation of Solution

[CH3NH3+]=2.50×10-3mol0.0500L=5.00×10-2MThehydrolysisofCH3NH3+isCH3NH3+(aq)H+(aq)+CH3NH3Cl(aq)Initialconcentration (M):   5.000 ×10-2  0              0Changeinconcentration (M):  -x    +x  +xEquilibriumconcentration(M):  (5.000 ×10-2)-xx           xKa=[CH3NH2][H+][CH3NH3+]2.3×10-11=x2(5.00×10-2)-x»x25.00×10-2      x2=1.15×10-12         x = 1.07×10-6M = [H+]        pH=-log[H+] = -log[1.07×10-6]=5.97 

The concentration of hydrogen ion is calculated from acid dissociation constant (Ka).  Using the concentration of hydrogen ion, the pH is determined by taking negative logarithm of concentration of hydrogen ion.

(c)

Interpretation Introduction

Interpretation:

The pH of titration HClVsCH3NH2 has to be calculated.

Concept introduction:

  • Titration is used to find out the strength of an unknown solution from a concentration of known solution.  A standard solution whose concentration is known, is dropped slowly to an unknown solution and wait for the chemical reaction finish.
  • The point at which amount of standard solution and analyte becomes equal and neutralisation happens in titration is called equivalence point.
  • pH is the logarithm of the reciprocal of the concentration  of H3O+  in a solution.
  •  pH is used to determine the acidity of an aqueous solution.

To calculate: pH of 25.0 mL of 0.100MHCl Vs35.0 mL of 0.100 MCH3NH2

(c)

Expert Solution
Check Mark

Answer to Problem 17.68QP

  pH = 10.24

Explanation of Solution

  HCl(aq) +CH3NH2(aq)CH3NH3Cl(aq)Initialconcentration (M):   2.50 ×10-3   3.50 ×10-3               0Changeinconcentration (M):  -2.50 ×10-3    -2.50 ×10-3  +2.50 ×10-3Final concentration(M):  01.00 ×10-3         2.50 ×10-3pH=pKa+log[conjugate base][acid]pH=-log(2.3×10-11)+log(1.00×10-3)(2.50×10-3)=10.24

The pH is calculated using Henderson-hasselbalch equation.  By substituting the value of concentration of base and acid and taking logarithm the pH is determined.

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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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