IB Chemistry Topic R3.1.17 the Ph of a Buffer Solution Revision Notes (HL)

IB Chemistry Topic R3.1.17 the Ph of a Buffer Solution Revision Notes (HL) | RevisionDojo

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Factors Affecting Buffer pH

Note

In this article, we use the Henderson-Hasselbalch equation to reason the intuition behind buffer pH.
In IB Chemistry (First Examination 2025), you don't have to remember this equation.
However, according to the syllabus, it is essential to understand that the pH of a buffer solution depends on both:
- the $pK_a$ of the weak acid or the $pK_b$ of the weak base in the conjugate pair
- the ratio of the concentration of the weak acid to its conjugate base, or the weak base to its conjugate acid.

The Henderson-Hasselbalch Equation: A Tool for Predicting Buffer pH

As discussed earlier, buffers consist of a weak acid and its conjugate base (or a weak base and its conjugate acid), which work together to resist pH changes.
The precise pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: $$\text{pH} = \text{p}K_a + \log{\frac{[\text{A}^-]}{[\text{HA}]}}$$ where:
1. $[A^-]$: Concentration of the conjugate base.
2. $[HA]$: Concentration of the weak acid.
3. $\text{pKa}$: The negative logarithm of the acid dissociation constant $K_a$ of the weak acid.

Note

This equation highlights two critical factors influencing buffer pH:

the $ \text{pKa} $ of the weak acid
the ratio of the concentrations of the conjugate base $[A^-]$ to the weak acid $[HA]$

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Factors Affecting Buffer pH

Note

In this article, we use the Henderson-Hasselbalch equation to reason the intuition behind buffer pH.
In IB Chemistry (First Examination 2025), you don't have to remember this equation.
However, according to the syllabus, it is essential to understand that the pH of a buffer solution depends on both:
- the $pK_a$ of the weak acid or the $pK_b$ of the weak base in the conjugate pair
- the ratio of the concentration of the weak acid to its conjugate base, or the weak base to its conjugate acid.

The Henderson-Hasselbalch Equation: A Tool for Predicting Buffer pH

As discussed earlier, buffers consist of a weak acid and its conjugate base (or a weak base and its conjugate acid), which work together to resist pH changes.
The precise pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: $$\text{pH} = \text{p}K_a + \log{\frac{[\text{A}^-]}{[\text{HA}]}}$$ where:
1. $[A^-]$: Concentration of the conjugate base.
2. $[HA]$: Concentration of the weak acid.
3. $\text{pKa}$: The negative logarithm of the acid dissociation constant $K_a$ of the weak acid.

Note

This equation highlights two critical factors influencing buffer pH:

the $ \text{pKa} $ of the weak acid
the ratio of the concentrations of the conjugate base $[A^-]$ to the weak acid $[HA]$

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Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

IB Chemistry R3.1.17 the Ph of a Buffer Solution Notes

Factors Affecting Buffer pH

The Henderson-Hasselbalch Equation: A Tool for Predicting Buffer pH

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Factors Affecting Buffer pH

The Henderson-Hasselbalch Equation: A Tool for Predicting Buffer pH

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics