Glossary
Buffer Capacity
The amount of strong acid or strong base that a buffer solution can neutralize before its pH changes significantly.
Example:
A large volume of a concentrated buffer will have a higher buffer capacity than a small volume of a dilute buffer, meaning it can absorb more added acid or base.
Buffers
Solutions that resist significant changes in pH when small amounts of strong acids or bases are added, maintaining a relatively stable pH.
Example:
Your blood contains a complex buffer system, primarily involving carbonic acid and bicarbonate ions, to keep its pH within a narrow range vital for enzyme function.
Conjugate Acid
The species formed when a weak base accepts a proton (H+); it is capable of donating a proton to reform the base.
Example:
When ammonia (NH₃) accepts a proton, it forms the ammonium ion (NH₄⁺), which is its conjugate acid and a key component in ammonium-based buffers.
Conjugate Base
The species formed when a weak acid donates a proton (H+); it is capable of accepting a proton to reform the acid.
Example:
When hydrofluoric acid (HF) loses a proton, it forms the fluoride ion (F-), which acts as its conjugate base in a buffer system.
Henderson-Hasselbalch Equation
An equation used to calculate the pH of a buffer solution, relating pH to the pKa of the weak acid and the ratio of the concentrations of the conjugate base to the weak acid.
Example:
To determine the pH of a buffer made from acetic acid and sodium acetate, you would use the Henderson-Hasselbalch equation with the pKa of acetic acid and the concentrations of both components.
Maximum Buffer Capacity
The point at which a buffer solution is most effective at resisting pH changes, occurring when the concentrations of the weak acid and its conjugate base are equal.
Example:
A chemist designing a buffer for a specific reaction would aim for maximum buffer capacity by ensuring the concentrations of the acid and its conjugate base are identical.
Strong Acid
An acid that completely dissociates in water, releasing all of its hydrogen ions into the solution.
Example:
Hydrochloric acid (HCl) is a strong acid commonly used in laboratories; when added to water, every HCl molecule breaks apart into H+ and Cl- ions.
Strong Base
A base that completely dissociates in water, releasing all of its hydroxide ions into the solution.
Example:
Sodium hydroxide (NaOH), a component of drain cleaner, is a strong base that fully dissociates into Na+ and OH- ions when dissolved in water.
Weak Acid
An acid that only partially dissociates in water, meaning it does not donate all of its hydrogen ions to the solution.
Example:
Acetic acid (CH₃COOH), found in vinegar, is a weak acid because only a small fraction of its molecules ionize in water.
Weak Base
A base that only partially ionizes in water, meaning it does not accept all available hydrogen ions.
Example:
Ammonia (NH₃) is a common weak base used in household cleaners, as it only partially reacts with water to produce hydroxide ions.
pH
A measure of the acidity or alkalinity of a solution, defined as the negative logarithm of the hydrogen ion concentration.
Example:
Lemon juice has a low pH (around 2-3), indicating its high acidity, while baking soda solution has a high pH (around 9), indicating its basicity.