Glossary
Arrhenius Acid
A substance that increases the concentration of hydrogen ions (H+) when dissolved in an aqueous solution.
Example:
When nitric acid, HNO₃, dissolves in water, it releases H+ ions, making it an Arrhenius acid.
Arrhenius Base
A substance that increases the concentration of hydroxide ions (OH-) when dissolved in an aqueous solution.
Example:
Potassium hydroxide, KOH, is an Arrhenius base because it dissociates in water to produce OH- ions.
Brønsted-Lowry Acid
A species that donates a proton (H+) in a chemical reaction.
Example:
In the reaction H₂SO₄ + H₂O → HSO₄⁻ + H₃O⁺, sulfuric acid (H₂SO₄) acts as a Brønsted-Lowry acid by donating a proton to water.
Brønsted-Lowry Base
A species that accepts a proton (H+) in a chemical reaction.
Example:
In the reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, ammonia (NH₃) acts as a Brønsted-Lowry base by accepting a proton from water.
Conjugate Acid
The species formed when a Brønsted-Lowry base accepts a proton.
Example:
When the base NH₃ accepts a proton, it forms NH₄⁺, which is its conjugate acid.
Conjugate Base
The species formed when a Brønsted-Lowry acid donates a proton.
Example:
When the acid HCl donates a proton, it forms Cl⁻, which is its conjugate base.
Hydronium Ion (H3O+)
The ion formed when a hydrogen ion (H+) associates with a water molecule, representing the actual form of H+ in aqueous solutions.
Example:
When hydrochloric acid dissolves in water, it forms hydronium ions, H₃O⁺, which are responsible for the solution's acidic properties.
Kw (Ion-product constant for water)
The equilibrium constant for the autoionization of water, representing the product of the hydronium ion and hydroxide ion concentrations.
Example:
At 25°C, the Kw value is 1.0 × 10⁻¹⁴, which means that in pure water, [H₃O⁺] and [OH⁻] are both 1.0 × 10⁻⁷ M.
pH
A measure of the acidity or basicity of an aqueous solution, defined as the negative logarithm (base 10) of the hydrogen ion (or hydronium ion) concentration.
Example:
A solution with a hydrogen ion concentration of 1.0 x 10⁻⁴ M would have a pH of 4.0, indicating it is acidic.
pOH
A measure of the basicity or acidity of an aqueous solution, defined as the negative logarithm (base 10) of the hydroxide ion concentration.
Example:
If a solution has a hydroxide ion concentration of 1.0 x 10⁻² M, its pOH would be 2.0, meaning it is strongly basic.