Henderson and Hasselbalch Equation to calculate pH

This presentation gives an explanation about Henderson and Hasselbalch equation a fundamental concept in biochemistry. The equation is used to calculate pH of buffer solution which is essential in maintaining acid base balance.
Key topics covered are
Introduction
Equation and the components explanation
Buffer solution and their importance
Applications and uses of this equation
Problems based on this equation
Conclusion.

1. National Institute Of Technology Puducherry Course code : ED1201 Course name: Organic and analytical chemistry Topic : Henderson and Hasselbalch Equation Submitted by S. Kamalini Ed24b1021 B.sc.B.ed ( itep ) physics major Submitted to Mr. S. Detchanamurthy Faculty of chemistry Department of education

2. INTRODUCTION A mathematical formula which relates pH, pKa , and the concentration of an acid and its conjugate base. An equation that could calculate the pH value of a given buffer solution was first derived by the American chemist Lawrence Joseph Henderson . This eqn. was then re-expressed in logarithmic terms by the Danish chemist Karl Albert Hasselbalch . The resulting eqn was named the HENDERSON-HASSELBALCH EQUATION.

3. EQUATION: pH = acidity of the solution pKa = negative logarithm of the acid dissociation constant [A] = concentration of the conjugate base [HA] = concentration of the acid

4. Derivation:

5. Significance: Why it is important? Used to calculate the pH of buffer solutions A buffer is a solution tat resist pH changes upon the addition of acidic or basic components This buffer solution is important for processes or reaction which require specific and stable pH ranges It helps in understanding acid-base equilibria in biological systems.

6. Applications: Uses BIOCHEMISTRY: 1. Helps in calculating the pH of buffer solutions, maintaining the stable pH in biochemical reactions 2. Understanding the optimal pH range of enzyme activity. MEDICINE: 3.Blood pH Regulation 4. Drug Formulation

7. Uses: CLINICAL LABORATORY: 5. Electrolyte balance: Used in assessing the acid-base balance in patient blood samples, helping diagnose various medical conditions. 6. Metabolic and Respiratory Disorders ENVIRONMENTAL SCIENCE : 7. Aquatic systems: Evaluates the buffer capacity of natural water bodies, important for assessing ecosystem health 8. Soil chemistry: Assists in understanding the pH balance in soils, which affects nutrient availability for plants

8. Uses: FOOD SCIENCE : Fermentation Processes: Helps monitor pH during fermentation, which is crucial for product quality in foods and beverages.

9. LIMITATIONS: Only valid for weak acids and bases: The eqn is applicable primarily to weak acids and their conjugate bases. For strong acids or bases, which completely dissociate in solution, the relationship does not hold. Not accurate at very high or very low concentrations. pH range limitations: The equation is most accurate when the ratio is between 0.1 and 10. Outside this range, the assumption that the concentrations of the species can adequately describe the pH may break down Temperature dependence: The pKa values are temperature dependent. Non-constant pKa : For some weak acids, the pKa can change with pH due to the formation of different species.

10. PROBLEMS: You have a buffer solution containing 0.1M acetic acid (HA) and 0.1M sodium acetate (A-). The pKa of acetic acid is 4.76. What is the pH of the buffer solution? You have a buffer solution composed of 0.05M ammonia (NH3) and 0.03M ammonium chloride (NH4Cl). The pKa of the ammonium ion (NH4+) is 9.25. What is the pH of this buffer solution? You have a buffer solution containing 0.2M acetic acid (CH3COOH) and 0.1M sodium acetate (CH3COONa). The pKa of acetic acid is 4.76. Calculate the pH of the buffer solution after adding 0.01 moles of NaOH to 1 litre of the buffer.

11. CONCLUSION: The Henderson-Hasselbalch equation is a key tool in biochemistry and medicine for understanding and calculating pH in buffer systems. It is a valuable tool for estimating pH in certain contexts, its applicability is limited, and care should be taken when using it, particularly under non-ideal conditions or with strong acids or bases. REFERENCE: Biophysical Chemistry – James P. Allen Essential Equations for Anaesthesia Key clinical concepts – Cambridge University Press

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