Search results for “pH”

pH Acids, Bases & Salts Dimensionless The negative logarithm to base ten of the hydrogen ion concentration, measuring the acidity of a solution. pH = −log[H⁺]

pH Scale Acids, Bases & Salts Dimensionless The conventional scale, usually running from 0 to 14, on which the acidity or alkalinity of aqueous solutions is expressed. 0 (acidic) – 7 (neutral) – 14 (alkaline)

Phase Diagram States of Matter & Gas Laws Pa, K A pressure–temperature plot showing which phase of a substance is thermodynamically stable under any given conditions.

Phase Equilibrium Chemical Equilibrium Dimensionless The condition in which two or more phases of a substance coexist with no net transfer between them. μ_phase1 = μ_phase2

Phenol Organic Chemistry Dimensionless A compound in which a hydroxyl group is bonded directly to an aromatic ring. C₆H₅–OH

Phenolphthalein Acids, Bases & Salts Dimensionless An acid–base indicator that is colourless in acid and pink in alkaline solution, changing between pH 8.3 and 10.0. C₂₀H₁₄O₄

Phospholipid Biochemistry & Polymer Chemistry Dimensionless A lipid in which one fatty acid of a triglyceride is replaced by a phosphate-containing group.

Photochemical Quantum Yield Chemical Kinetics & Catalysis Dimensionless The number of molecules reacting for each photon of light absorbed by the system. Φ = molecules reacted / photons absorbed

Photochemical Reaction Stoichiometry & Chemical Reactions nm A reaction initiated by the absorption of light, which promotes a molecule to an electronically excited state. A + hν → A*

Photosynthesis Biochemistry & Polymer Chemistry kJ/mol The process by which plants use light energy to convert carbon dioxide and water into carbohydrate and oxygen. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Physical Change Foundations of Chemistry Dimensionless A change that alters the form or state of a substance while leaving its chemical composition intact.

Physical Equilibrium Chemical Equilibrium Dimensionless An equilibrium between two physical states or phases of the same substance. H₂O(l) ⇌ H₂O(g)

Physical Property Foundations of Chemistry Various A characteristic of a substance that can be observed or measured without altering its chemical identity.

Physisorption Chemical Kinetics & Catalysis kJ/mol Weak adsorption in which molecules are held to a surface by van der Waals forces alone. ΔH ≈ −20 to −40 kJ/mol

Polymorphism States of Matter & Gas Laws Dimensionless The ability of a single substance to exist in more than one crystalline form.

Partition Coefficient Chemical Equilibrium Dimensionless The equilibrium ratio of a solute's concentrations in two immiscible phases. P = C₁ / C₂

Plum Pudding Model Atomic Structure & Periodicity Dimensionless J. J. Thomson's 1904 model picturing the atom as a sphere of diffuse positive charge with electrons embedded within it.

Pure Substance Foundations of Chemistry Dimensionless Matter with a fixed chemical composition and a definite set of physical properties, comprising either a single element or a single compound.

Packing Efficiency States of Matter & Gas Laws Dimensionless The percentage of the total volume of a unit cell that is actually occupied by the constituent particles. (volume of atoms / cell volume) × 100

Parts per Million Solutions & Colligative Properties ppm A concentration unit expressing one part of solute per million parts of solution by mass or volume. ppm = (m_solute / m_solution) × 10⁶

Penetrating Power Nuclear & Radiochemistry mm The depth to which a given type of radiation can travel into a material before being absorbed.

Percentage Purity Stoichiometry & Chemical Reactions Dimensionless The proportion of a sample that consists of the desired compound, expressed as a percentage of the total mass. % purity = (mass pure / mass sample) × 100

Percentage Yield Stoichiometry & Chemical Reactions Dimensionless The actual yield expressed as a percentage of the theoretical yield. % yield = (actual / theoretical) × 100

pKa Acids, Bases & Salts Dimensionless The negative logarithm of the acid dissociation constant, giving a convenient scale of acid strength. pKa = −log Ka

Results for “pH”