Phosphate-buffered saline (PBS) is a buffer solution frequently used in pharmaceutical practice, particularly in the formulation of ophthalmic solutions. It is also used in colorimetric determination of pH and in research studies where maintaining a constant pH is essential. Phosphate-buffered saline (PBS) contains sodium chloride (NaCl) and dibasic sodium phosphate (Na2HPO4). It may also contain […]
What Is A Buffer Solution? Buffer solution is a combination of a weak acid and its conjugate base (i.e., its salt) or a weak base and its conjugate acid acts as a buffer. If 1 mL of a 0.1 N HCl solution is added to 100 mL of pure water, the pH is reduced from […]
The Henderson-Hasselbalch equation is used in situations where both undissociated acids and their conjugate bases are present in a solution. This situation can occur by adding the conjugate base to a solution of a weak acid or by partially neutralizing the weak acid with a strong base. Mixtures of an undissociated weak acid and its […]
When a weak acid is dissolved in water, the acid will undergo ionization. The ionization of a weak acid, HA, in water can be expressed as: $$ HA+H_2O⇄H^++A^- $$ Four species are present in the solution of the weak acid at equilibrium: HA, A−, H+, and OH−. To calculate the concentrations of the four species […]
When a strong acid (e.g., HCl) is placed in water, the acid ionizes completely as: $$ HCl+H_2O→H^++Cl^- $$ Three species are present in the aqueous solution of the strong acid: H+, OH–, and Cl–. H+, generated from HCl, suppresses the ionization of H2O. This leads to the lower concentration of H+ in water than the […]
The hydrogen ion concentration of a solution varies from approximately 1 in a 1 M solution of a strong acid to about 1×10-14 in a 1 M solution of a strong base, and the calculations often become unwieldy. To alleviate this difficulty, Sörensen suggested a simplified method of expressing hydrogen ion concentration. He established the […]
The concentration of hydrogen or hydroxyl ions in solutions of acids or bases may be expressed as gram-ions per liter or as moles per liter. A solution containing 17.008 g of hydroxyl ions or 1.008 g of hydrogen ions per liter is said to contain 1 gram-ion or 1 mole of hydroxyl or hydrogen ions […]
A weak base is one that, when dissolved in water, only partially dissociates. As a result, the aqueous solution contains a relatively small amount of hydroxide ions and the corresponding base ions, while most of the base remains in its undissociated molecular form. Common examples of weak bases include ammonia (NH3), baking soda (sodium bicarbonate, […]
Weak acids are acids that do not completely dissociate into their ions when dissolved in water. Instead, they partially ionize, meaning only a fraction of the acid molecules release hydrogen ions (H+) into the solution. The rest of the molecules remain in their undissociated form. This creates an equilibrium between the undissociated acid and its […]
Theories of acids and bases have evolved over time to explain their chemical behavior and interactions in various contexts. The most prominent theories include Arrhenius, Brønsted-Lowry, and Lewis theories. Each theory builds upon its predecessors, providing deeper insight into the nature of acids and bases. Below is an introduction to these major theories: Arrhenius Theory […]