Explanation a) 2 M acetic acid and 2 M sodium acetate. Consider the degree of dissociation to be x . The ionization reaction and the ICE table is represented below. CH 3 COOH ( aq ) ⇌ H + ( aq ) + CH 3 COO − ( aq ) Initial ( M ) 2 0 2 Change ( M ) 2 − x + x 2 + x Equilibrium ( M ) 2 − x + x 2 + x The equilibrium expression for the reaction is as shown below: K a = [CH 3 COO − ][H + ] [ CH 3 COOH ] Here, K a is the equilibrium constant. The concentrations of acetate ion, acetic acid, and hydrogen ion are represented by [ CH 3 COO − ] , [ CH 3 COOH ] , and [ H + ] , respectively. The acid dissociation constant of acetic acid is 1 .8 × 10 − 5 . The value of x is very small as compared to 2 and hence, it can be neglected. Substitute the values of the concentrations in the above expression as shown below, K a = [H + ](2 + x ) (2 .0 − x ) ≈ [ H + ] ( 2 ) ( 2 ) = [ H + ] Take minus log on both sides of the above expression. − log(K a ) = − log([H + ]) pK a = pH Substitute the value of the dissociation constant in the above expression, pH = − log ( 1.8 × 10 − 5 ) = 4.74 pH = 4.74 Hence, pH = 4.74 Another methodforcalculating the pH of a buffer solution isgiven by the Henderson–Hasselbalach equation. The expression for the pH for an acidic buffer is as follows: pH = pK a + log [Conjugate Base] [Weak Acid] pH = − log ( K a ) + log [2] [2] = − log ( 1.8 × 10 − 5 ) = 4.74 Hence, the pH of the solution has been calculated. b) 0.20 M acetic acid and 0.20 M sodium acetate Consider the degree of dissociation to be x

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ISBN: 9781259137815

Author: Julia Burdge

Publisher: McGraw-Hill Education

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Acid Base Titration

An acid-base titration is the method of quantitative analysis for determining the concentration of an acid and base by exactly neutralizing it with a standard solution of base or acid having known concentration.

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Chapter 17, Problem 10QP

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Interpretation:

The pH for the given buffer solutions is to be calculated. Also, the more effective buffer and the reason for its effectiveness are to be determined.

Concept introduction:

Buffers are the solutionsthat resist the change in the pH on the addition of a few amounts of the acid and the alkali. It isa mixture of a weak acid with its conjugate base or a weak base with its conjugate acid.

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Chapter 17, Problem 9QP

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Chapter 17 Solutions

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Ch. 17.1 - Practice ProblemATTEMPT Determine the pH at 25°C...Ch. 17.1 - Practice ProblemBUILD Determine the pH at 25°C of...Ch. 17.1 - Prob. 1PPC Ch. 17.1 - Which of the following would cause a decrease in...Ch. 17.1 - What is the pH of a solution prepared by adding 0...Ch. 17.2 - Practice Problem ATTEMPT Calculate the pH of 1 L...Ch. 17.2 - Practice Problem BUILD How much must be added to...Ch. 17.2 - Practice Problem CONCEPTUALIZE The first diagram...Ch. 17.2 - 17.2.1 Which of the following combinations can be...Ch. 17.2 - What is the pH of a buffer that is 0.76 M in HF...

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Solution Summary: The author explains that buffers are solutions that resist the change in pH on the addition of a few amounts of the acid and the alkali.

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