Buffers and Equilibria

Front

Chemical Equilibrium Noun

---

[kem-i-kuhl ee-kwuh-lib-ree-uhm]

Back

Chemical Equilibrium

---

A state where the rates of the forward and reverse reactions are equal, resulting in no net change in concentrations.

---

Example: This graph shows that in a chemical reaction, reactants decrease and products increase until equilibrium is reached, where their concentrations become constant over time.

Front

pH Noun

---

[pee-eych]

Back

pH

---

A scale used to specify the acidity or basicity of an aqueous solution based on hydronium ion concentration.

---

Example: The pH scale measures how acidic or alkaline a substance is, from 0 (very acidic) to 14 (very alkaline), with 7 being neutral.

Front

Buffer System Noun

---

[buf-er sis-tuhm]

Back

Buffer System

---

A mixture of a weak acid and its conjugate base that works to resist changes in a solution's pH.

---

Example: When acid (H+) is added to a buffer solution, a component of the buffer absorbs the acid, preventing a large change in the solution's properties.

Front

Weak Acid Noun

---

[week as-id]

Back

Weak Acid

---

An acid that only partially dissociates or ionizes when dissolved in an aqueous solution, establishing an equilibrium.

---

Example: A weak acid (HA) only partially breaks apart (dissociates) in water, so at equilibrium, most of it remains as HA molecules with only a few H+ and A- ions.

Front

Conjugate Base Noun

---

[kon-juh-git beys]

Back

Conjugate Base

---

The chemical species that is formed after an acid has donated a proton during a chemical reaction.

---

Example: When an acid (HCl) donates a proton (H+), the remaining part (Cl⁻) is called its conjugate base, forming a related pair.

Front

Weak Base Noun

---

[week beys]

Back

Weak Base

---

A base that only partially dissociates or ionizes when dissolved in an aqueous solution, establishing an equilibrium.

---

Example: A weak base only partially breaks apart (dissociates) in water, meaning most of it remains as whole molecules with only a few resulting ions.

Front

Conjugate Acid Noun

---

[kon-juh-git as-id]

Back

Conjugate Acid

---

The chemical species that is formed after a base has accepted a proton during a chemical reaction.

---

Example: This diagram shows a base (B) taking a proton (H) from an acid (HA). After accepting the proton, the base becomes a conjugate acid (HB+).

Front

Hydronium Ion Noun

---

[hahy-droh-nee-uhm ahy-on]

Back

Hydronium Ion

---

The ion (H3O+) formed when a water molecule accepts a proton; its concentration determines a solution's acidity.

---

Example: This diagram shows a water molecule combining with a proton (a hydrogen ion) to form a positively charged hydronium ion (H₃O⁺).

Front

Hydroxide Ion Noun

---

[hahy-drok-sahyd ahy-on]

Back

Hydroxide Ion

---

The ion (OH-) whose concentration in a solution determines its alkalinity or basicity.

---

Example: A hydroxide ion is made of one oxygen atom bonded to one hydrogen atom, and it carries an overall negative charge.

Front

Ethanoic Acid Noun

---

[eth-uh-noh-ik as-id]

Back

Ethanoic Acid

---

A common weak acid (CH3COOH), also known as acetic acid, that is frequently used in buffer system examples.

---

Example: This diagram shows the arrangement of carbon, hydrogen, and oxygen atoms that form a molecule of ethanoic acid, a key component in buffer solutions.