Chemistry: The Molecular Science
Chemistry: The Molecular Science
5th Edition
ISBN: 9781285199047
Author: John W. Moore, Conrad L. Stanitski
Publisher: Cengage Learning
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Chapter 14, Problem 121QRT
Interpretation Introduction

Interpretation:

The pHof0.00500MNH4[B(OH)4] has to be calculated (a) by using the simplifying assumption regarding x, (b) by solving a quadratic equation and (c) by using the method of successive approximations.

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Answer to Problem 121QRT

The pHof0.00500MNH4[B(OH)4] (a) by using the simplifying assumption regarding x is 10.46, (b) by solving a quadratic equation is 10.45 and (c) by using the method of successive approximations is 10.45.

Explanation of Solution

The solution contains NH4+ and [B(OH)4] ions.  Ka for NH4+ is 5.6×1010 and Kb for [B(OH)4] is 1.7×105.  As Kb>Ka, the solution is basic.

The equation for the equilibrium can be written as given below.

  B(OH)4(aq)+H2O(l)B(OH)3H2O(aq)+OH(aq)

The basic ionization constant for the above equation can be written as given below.

  Kb=[B(OH)3(H2O)][OH][B(OH)3]

A table can be set up as given below.

B(OH)4(aq)B(OH)3H2O(aq)OH(aq)Initialconc.(M)0.0050001.0×107Changeinconc.(M)x+x+xEquilibriumconc.(M)0.00500xxx

The concentration of OH comes from its auto ionization that is 1.0×107.  It can be assumed to be small compared to the change.

By substituting all the values in the above equation, the value of x can be calculated.

  Kb=(x)(x)(0.00500x)=1.7×105

(a) Assuming x is very small, it can be written as 0.00500x0.00500.

Then,

  x2=(1.7×105)(0.00500)x=2.9×104M=[OH]

The pH of the solution can be calculated as follows,

  pOH=log[OH]=log(2.9×104)=3.54.pH=14.00pOH=14.003.54=10.46.

Therefore, the pHof0.00500MNH4[B(OH)4] is 10.46.

(b) The above equation can be rearranged in the form of a quadratic equation as shown below.

  x2=(1.7×105)(0.00500x)x2+(1.7×105)x8.5×108=0x=2.8×104=[OH]

The pH of the solution can be calculated as follows,

  pOH=log[OH]=log(2.8×104)=3.55.pH=14.00pOH=14.003.55=10.45.

Therefore, the pHof0.00500MNH4[B(OH)4] is 10.45.

(c) using the method of successive approximations, it can be written as given below.

  0.00500x=0.005002.9×104M=0.00471M.

Now,

  x2=(1.7×105)(0.00471)x=2.8×104M=[OH]

The pH of the solution can be calculated as follows,

  pOH=log[OH]=log(2.8×104)=3.55.pH=14.00pOH=14.003.55=10.45.

Therefore, the pHof0.00500MNH4[B(OH)4] is 10.45.

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Chapter 14 Solutions

Chemistry: The Molecular Science

Ch. 14.4 - Calculate the pH of a 0.040-M NaOH solution. Ch. 14.4 - In a hospital laboratory the pH of a bile sample...Ch. 14.4 - Prob. 14.8CECh. 14.4 - Prob. 14.9ECh. 14.4 - Prob. 14.10ECh. 14.5 - Write the ionization equation and ionization...Ch. 14.5 - Write the ionization equation and the Kb...Ch. 14.5 - Prob. 14.11CECh. 14.5 - Prob. 14.12CECh. 14.5 - Prob. 14.13ECh. 14.6 - Prob. 14.14CECh. 14.6 - Prob. 14.15CECh. 14.6 - Prob. 14.16CECh. 14.6 - Prob. 14.17CECh. 14.6 - Prob. 14.18CECh. 14.7 - Lactic acid is a monoprotic acid that occurs...Ch. 14.7 - Prob. 14.9PSPCh. 14.7 - Prob. 14.19ECh. 14.7 - Prob. 14.10PSPCh. 14.7 - Prob. 14.20ECh. 14.8 - Prob. 14.11PSPCh. 14.8 - Prob. 14.21CECh. 14.8 - Prob. 14.12PSPCh. 14.8 - Prob. 14.22ECh. 14.8 - Prob. 14.23CECh. 14.8 - Prob. 14.24CECh. 14.9 - Predict whether each of these is a Lewis acid or a...Ch. 14.9 - Prob. 14.26ECh. 14.9 - Prob. 14.27ECh. 14.10 - Prob. 14.28ECh. 14.10 - Prob. 14.13PSPCh. 14.10 - Prob. 14.29ECh. 14.10 - Calculate the pH of 5.2-M aqueous sodium...Ch. 14 - Lactic acid, CH3CH(OH)COOH, is a weak monoprotic...Ch. 14 - Define a Brnsted-Lowry acid and a Brnsted-Lowry...Ch. 14 - Prob. 2QRTCh. 14 - Prob. 3QRTCh. 14 - Prob. 4QRTCh. 14 - Prob. 5QRTCh. 14 - Prob. 6QRTCh. 14 - Prob. 7QRTCh. 14 - Prob. 8QRTCh. 14 - Write a chemical equation to describe the proton...Ch. 14 - Write a chemical equation to describe the proton...Ch. 14 - Prob. 11QRTCh. 14 - Prob. 12QRTCh. 14 - Prob. 13QRTCh. 14 - Prob. 14QRTCh. 14 - Prob. 15QRTCh. 14 - Prob. 16QRTCh. 14 - Prob. 17QRTCh. 14 - Prob. 18QRTCh. 14 - Prob. 19QRTCh. 14 - Prob. 20QRTCh. 14 - Prob. 21QRTCh. 14 - Prob. 22QRTCh. 14 - Prob. 23QRTCh. 14 - Formic acid, HCOOH, is found in ants. Write a...Ch. 14 - Milk of magnesia, Mg(OH)2, has a pH of 10.5....Ch. 14 - A sample of coffee has a pH of 4.3. Calculate the...Ch. 14 - Calculate the pH of a solution that is 0.025-M in...Ch. 14 - Calculate the pH of a 0.0013-M solution of HNO3....Ch. 14 - Prob. 29QRTCh. 14 - Prob. 30QRTCh. 14 - A 1000.-mL solution of hydrochloric acid has a pH...Ch. 14 - Prob. 32QRTCh. 14 - Prob. 33QRTCh. 14 - Prob. 34QRTCh. 14 - Figure 14.3 shows the pH of some common solutions....Ch. 14 - Figure 14.3 shows the pH of some common solutions....Ch. 14 - The measured pH of a sample of seawater is 8.30....Ch. 14 - Prob. 38QRTCh. 14 - Valine is an amino acid with this Lewis structure:...Ch. 14 - Leucine is an amino acid with this Lewis...Ch. 14 - Prob. 41QRTCh. 14 - Prob. 42QRTCh. 14 - Prob. 43QRTCh. 14 - Prob. 44QRTCh. 14 - Prob. 45QRTCh. 14 - Prob. 46QRTCh. 14 - Prob. 47QRTCh. 14 - Prob. 48QRTCh. 14 - Prob. 49QRTCh. 14 - Prob. 50QRTCh. 14 - Prob. 51QRTCh. 14 - Prob. 52QRTCh. 14 - Prob. 53QRTCh. 14 - Prob. 54QRTCh. 14 - A 0.015-M solution of cyanic acid has a pH of...Ch. 14 - Prob. 56QRTCh. 14 - The pH of a 0.10-M solution of propanoic acid,...Ch. 14 - Prob. 58QRTCh. 14 - Prob. 59QRTCh. 14 - Prob. 60QRTCh. 14 - Prob. 61QRTCh. 14 - Amantadine, C10H15NH2, is a weak base used in the...Ch. 14 - Prob. 63QRTCh. 14 - Lactic acid, C3H6O3, occurs in sour milk as a...Ch. 14 - Prob. 65QRTCh. 14 - Complete each of these reactions by filling in the...Ch. 14 - Complete each of these reactions by filling in the...Ch. 14 - Predict which of these acid-base reactions are...Ch. 14 - Predict which of these acid-base reactions are...Ch. 14 - Prob. 70QRTCh. 14 - Prob. 71QRTCh. 14 - Prob. 72QRTCh. 14 - Prob. 73QRTCh. 14 - Prob. 74QRTCh. 14 - Prob. 75QRTCh. 14 - Prob. 76QRTCh. 14 - Prob. 77QRTCh. 14 - Prob. 78QRTCh. 14 - Prob. 79QRTCh. 14 - Prob. 80QRTCh. 14 - Prob. 81QRTCh. 14 - Trimethylamine, (CH3)3N, reacts readily with...Ch. 14 - Prob. 83QRTCh. 14 - Prob. 84QRTCh. 14 - Prob. 85QRTCh. 14 - Prob. 86QRTCh. 14 - Common soap is made by reacting sodium carbonate...Ch. 14 - Prob. 88QRTCh. 14 - Prob. 89QRTCh. 14 - Prob. 90QRTCh. 14 - Prob. 91QRTCh. 14 - Prob. 92QRTCh. 14 - Prob. 93QRTCh. 14 - Several acids and their respective equilibrium...Ch. 14 - Prob. 95QRTCh. 14 - Prob. 96QRTCh. 14 - Does the pH of the solution increase, decrease, or...Ch. 14 - Does the pH of the solution increase, decrease, or...Ch. 14 - Prob. 99QRTCh. 14 - Prob. 100QRTCh. 14 - Prob. 101QRTCh. 14 - Prob. 102QRTCh. 14 - Prob. 103QRTCh. 14 - Prob. 104QRTCh. 14 - Prob. 105QRTCh. 14 - Prob. 106QRTCh. 14 - When all the water is evaporated from a sodium...Ch. 14 - Prob. 108QRTCh. 14 - Prob. 109QRTCh. 14 - Prob. 110QRTCh. 14 - Prob. 111QRTCh. 14 - Prob. 112QRTCh. 14 - Prob. 113QRTCh. 14 - Prob. 114QRTCh. 14 - Prob. 115QRTCh. 14 - Prob. 116QRTCh. 14 - Home gardeners spread aluminum sulfate powder...Ch. 14 - Prob. 118QRTCh. 14 - Prob. 119QRTCh. 14 - Prob. 120QRTCh. 14 - Prob. 121QRTCh. 14 - Prob. 122QRTCh. 14 - Prob. 123QRTCh. 14 - Prob. 124QRTCh. 14 - Prob. 125QRTCh. 14 - A chilled carbonated beverage is opened and warmed...Ch. 14 - Prob. 127QRTCh. 14 - Explain why BrNH2 is a weaker base than ammonia,...Ch. 14 - Prob. 129QRTCh. 14 - Prob. 130QRTCh. 14 - At 25 C, a 0.10% aqueous solution of adipic acid,...Ch. 14 - Prob. 132QRTCh. 14 - Prob. 133QRTCh. 14 - Prob. 134QRTCh. 14 - Prob. 135QRTCh. 14 - Prob. 14.ACPCh. 14 - Develop a set of rules by which you could predict...
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