Acid-base chemistry

= Acid-Base Chemistry =

Acid-base chemistry is a fundamental concept in chemistry that deals with the properties and reactions of acids and bases. Understanding acid-base chemistry is crucial for medical students as it plays a significant role in physiological processes and clinical medicine.

Definitions

Acids

An acid is a substance that can donate a proton (H⁺ ion) to another substance. According to the Brønsted-Lowry definition, acids are proton donors. The strength of an acid is determined by its ability to donate protons.

Bases

A base is a substance that can accept a proton. In the Brønsted-Lowry framework, bases are proton acceptors. The strength of a base is determined by its ability to accept protons.

pH Scale

The pH scale is a measure of the acidity or basicity of a solution. It is a logarithmic scale ranging from 0 to 14, with 7 being neutral. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic solution.

Acid-Base Theories

Arrhenius Theory

The Arrhenius theory defines acids as substances that increase the concentration of hydrogen ions (H⁺) in aqueous solution, while bases increase the concentration of hydroxide ions (OH⁻).

Brønsted-Lowry Theory

The Brønsted-Lowry theory expands on the Arrhenius definition by describing acids as proton donors and bases as proton acceptors, applicable in both aqueous and non-aqueous solutions.

Lewis Theory

The Lewis theory defines acids as electron pair acceptors and bases as electron pair donors. This theory broadens the concept of acids and bases beyond protons.

Acid-Base Reactions

Acid-base reactions involve the transfer of protons from acids to bases. These reactions can be represented by the general equation:

Acid + Base → Conjugate Base + Conjugate Acid

For example, in the reaction between hydrochloric acid (HCl) and ammonia (NH₃):

HCl + NH₃ → NH₄⁺ + Cl⁻

HCl donates a proton to NH₃, forming the conjugate base Cl⁻ and the conjugate acid NH₄⁺.

Buffer Systems

Buffers are solutions that resist changes in pH upon the addition of small amounts of acid or base. They are crucial in maintaining the pH of biological systems. A common buffer system in the human body is the bicarbonate buffer system, which maintains blood pH around 7.4.

Clinical Relevance

Acid-base balance is vital for normal physiological function. Imbalances can lead to conditions such as acidosis and alkalosis, which can be life-threatening if not corrected. Medical students must understand the mechanisms of acid-base homeostasis and the interpretation of arterial blood gases (ABGs) to diagnose and manage these conditions.

Conclusion

Acid-base chemistry is a cornerstone of both chemistry and medicine. A thorough understanding of the principles of acid-base reactions, buffer systems, and their physiological implications is essential for medical students and healthcare professionals.

References

• Atkins, P., & de Paula, J. (2010). Physical Chemistry. Oxford University Press.
• Alberty, R. A., & Silbey, R. J. (2001). Physical Chemistry. Wiley.
• Guyton, A. C., & Hall, J. E. (2006). Textbook of Medical Physiology. Elsevier Saunders.