Chemistry: An Atoms-Focused Approach (Second Edition)
Chemistry: An Atoms-Focused Approach (Second Edition)
2nd Edition
ISBN: 9780393614053
Author: Thomas R. Gilbert, Rein V. Kirss, Stacey Lowery Bretz, Natalie Foster
Publisher: W. W. Norton & Company
Question
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Chapter 15, Problem 15.105QA
Interpretation Introduction

To find:

The pKa of 0.125(M) aqueous solution of sodium propanoate

Expert Solution & Answer
Check Mark

Answer to Problem 15.105QA

Solution:

The pKa for 0.125M aquoues solution of sodium propionate is 8.97

Explanation of Solution

1) Concept:

Sodium propionate is a salt of strong base NaOH and weak acid CH3COOH.So it is a basic salt.Na+ ion has no role in its acid-base properties, they are spectator ions.

First, we have to find out the value of Ka from the given value of pKa.

Then, molar concentration of OH- ion has to be calculated using the RICE table for the hydrolysis of Sodium propanoate salt.

pOH is calculated using the molar concentration of OH-

And finally, we calculate pH from the pOH value.

2) Formula:

i) pKa=-logKa

ii) Kh=KwKa

iii) pOH=-logOH-

iv) pH= 14.00-pOH

3) Calculation:

Ka can be calculated as:

4.85=-logKa

Ka=1.41×10-5

Kh=KwKa =1.0×10-141.41×10-5=0.709×10-9

Now we have to calculate the molar concentration of CH3CH2COONa using RICE table:

Reaction:                CH3CH2COO-aq+H2Ol             CH3CH2COOH+OH-

Initial                                          0.125                                                    0                   0

Change                                        -x                                                    +x                  +x

Equilibrium                               (0.125-x)                                            x                   x

To solve for ‘x’, a simplifying assumption has to be made that ‘x’ is very small compared to 0.125M because CH3CH2COO-initial is 0.1250.709 ×10-9 = 0.176 ×109 times than Kb value, which is much greater than 500xguideline.

Kh=CH3CH2COOH[OH-]CH3CH2COO- = xx0.125-xx20.125=0.709×10-9

x=9.414×10-6

So, OH-=9.414×10-6(M)

Therefore, pOH=-log[9.414×10-6]=6-0.9737= 5.026

pH =14.00-5.026=8.97

Conclusion:

The pH of 0.125(M) aqueous solution of Sodium propanoateis 8.97

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Chapter 15 Solutions

Chemistry: An Atoms-Focused Approach (Second Edition)

Ch. 15 - Prob. 15.11QACh. 15 - Prob. 15.12QACh. 15 - Prob. 15.13QACh. 15 - Prob. 15.14QACh. 15 - Prob. 15.15QACh. 15 - Prob. 15.16QACh. 15 - Prob. 15.17QACh. 15 - Prob. 15.18QACh. 15 - Prob. 15.19QACh. 15 - Prob. 15.20QACh. 15 - Prob. 15.21QACh. 15 - Prob. 15.22QACh. 15 - Prob. 15.23QACh. 15 - Prob. 15.24QACh. 15 - Prob. 15.25QACh. 15 - Prob. 15.26QACh. 15 - Prob. 15.27QACh. 15 - Prob. 15.28QACh. 15 - Prob. 15.29QACh. 15 - Prob. 15.30QACh. 15 - Prob. 15.31QACh. 15 - Prob. 15.32QACh. 15 - Prob. 15.33QACh. 15 - Prob. 15.34QACh. 15 - Prob. 15.35QACh. 15 - Prob. 15.36QACh. 15 - Prob. 15.37QACh. 15 - Prob. 15.38QACh. 15 - Prob. 15.39QACh. 15 - Prob. 15.40QACh. 15 - Prob. 15.41QACh. 15 - Prob. 15.42QACh. 15 - Prob. 15.43QACh. 15 - Prob. 15.44QACh. 15 - Prob. 15.45QACh. 15 - Prob. 15.46QACh. 15 - Prob. 15.47QACh. 15 - Prob. 15.48QACh. 15 - Prob. 15.49QACh. 15 - Prob. 15.50QACh. 15 - Prob. 15.51QACh. 15 - Prob. 15.52QACh. 15 - Prob. 15.53QACh. 15 - Prob. 15.54QACh. 15 - Prob. 15.55QACh. 15 - Prob. 15.56QACh. 15 - Prob. 15.57QACh. 15 - Prob. 15.58QACh. 15 - Prob. 15.59QACh. 15 - Prob. 15.60QACh. 15 - Prob. 15.61QACh. 15 - Prob. 15.62QACh. 15 - Prob. 15.63QACh. 15 - Prob. 15.64QACh. 15 - Prob. 15.65QACh. 15 - Prob. 15.66QACh. 15 - Prob. 15.67QACh. 15 - Prob. 15.68QACh. 15 - Prob. 15.69QACh. 15 - Prob. 15.70QACh. 15 - Prob. 15.71QACh. 15 - Prob. 15.72QACh. 15 - Prob. 15.73QACh. 15 - Prob. 15.74QACh. 15 - Prob. 15.75QACh. 15 - Prob. 15.76QACh. 15 - Prob. 15.77QACh. 15 - Prob. 15.78QACh. 15 - Prob. 15.79QACh. 15 - Prob. 15.80QACh. 15 - Prob. 15.81QACh. 15 - Prob. 15.82QACh. 15 - Prob. 15.83QACh. 15 - Prob. 15.84QACh. 15 - Prob. 15.85QACh. 15 - Prob. 15.86QACh. 15 - Prob. 15.87QACh. 15 - Prob. 15.88QACh. 15 - Prob. 15.89QACh. 15 - Prob. 15.90QACh. 15 - Prob. 15.91QACh. 15 - Prob. 15.92QACh. 15 - Prob. 15.93QACh. 15 - Prob. 15.94QACh. 15 - Prob. 15.95QACh. 15 - Prob. 15.96QACh. 15 - Prob. 15.97QACh. 15 - Prob. 15.98QACh. 15 - Prob. 15.99QACh. 15 - Prob. 15.100QACh. 15 - Prob. 15.101QACh. 15 - Prob. 15.102QACh. 15 - Prob. 15.103QACh. 15 - Prob. 15.104QACh. 15 - Prob. 15.105QACh. 15 - Prob. 15.106QACh. 15 - Prob. 15.107QACh. 15 - Prob. 15.108QACh. 15 - Prob. 15.109QACh. 15 - Prob. 15.110QA
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