Ionic Equilibria and Buffers: Key Concepts for Pharmacology and Chemistry

What is an electrolyte?

An electrolyte is a substance (an acid, base, or salt) that ionizes in an aqueous solution to form positive ions (cations) and negative ions (anions).

What distinguishes strong electrolytes from weak electrolytes?

Strong electrolytes are completely ionized in water, while weak electrolytes only partially ionize.

Give an example of a strong electrolyte.

Hydrochloric acid (HCl) is an example of a strong electrolyte.

What are some examples of weak electrolytes?

Atropine, phenobarbital, and sulfadiazine are examples of weak electrolytes.

What are nonelectrolytes?

Nonelectrolytes are substances that do not ionize in water and do not conduct an electric current. Examples include sucrose, fructose, urea, and glycerol.

How does pH affect the ionization of weak electrolytes?

The degree of ionization of weak electrolytes varies with pH, affecting their absorption, transport, and excretion in the body.

What is the pH-partition hypothesis?

The pH-partition hypothesis states that the absorption of a weak electrolyte is determined by the extent to which the drug exists in its unionized form at the site of absorption.

What is the effect of a small change in pH on weak electrolytes?

A small change in pH can cause a large change in the ratio of ionized to unionized molecules, significantly affecting solubility and drug properties.

What are ionization constants used for?

Ionization constants (pKa) measure the strength of acids and bases and help calculate the extent of ionization of weak acids or bases at a given pH.

How is a salt formed?

A salt is formed by an acid-base reaction involving either proton donation or acceptance.

What determines the nature of a salt solution (neutral, acidic, or basic)?

The nature of a salt solution depends on the interaction of the ions of the salt with the ions of water, known as hydrolysis.

What are the four categories of salts?

1. Salts of strong acids and strong bases 2. Salts of weak acids and strong bases 3. Salts of strong acids and weak bases 4. Salts of weak acids and weak bases.

What is a buffer solution?

A buffer solution is a solution that resists changes in pH upon the addition of small amounts of acid or base.

What is the Henderson-Hasselbalch equation used for?

The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution.

What is buffer capacity?

Buffer capacity is the ability of a buffer solution to resist changes in pH upon the addition of acids or bases.

How can you calculate the quantity of ingredients needed to prepare a buffer solution?

The quantity of ingredients for a buffer solution can be calculated based on the desired pH and the molar ratio of the acid and its conjugate base.

What is the relationship between pKa and the strength of an acid?

A lower pKa value indicates a stronger acid, as it signifies a greater tendency to donate protons.

How does water behave in terms of acid-base chemistry?

Water can act as both an acid and a base, capable of losing or accepting protons.

What is the significance of the degree of ionization for drug absorption?

The degree of ionization affects the solubility and permeability of drugs, influencing their absorption and effectiveness.

What is the impact of ionization on drug stability?

The degree of ionization can affect the physicochemical stability of a drug product.

What are the components of a buffer solution?

A buffer solution typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid.

What happens to the pH of a buffer solution when an acid is added?

The pH of a buffer solution changes only slightly when an acid is added, demonstrating its buffering capacity.

What is the effect of ionic strength on ionization?

Ionic strength affects the degree of ionization of electrolytes, influencing their behavior in solution.

What is the role of ionization constants in drug formulation?

Ionization constants help predict the behavior of drugs in different pH environments, aiding in formulation and delivery.

What is the significance of the ratio of ionized to unionized forms of a drug?

The ratio of ionized to unionized forms determines the drug's solubility and permeability, impacting its therapeutic effectiveness.