Browse the dictionary
960 terms · page 31 of 40
Product
Stoichiometry & Chemical Reactions
mol
A substance formed as a result of a chemical reaction.
Promoter
Chemical Kinetics & Catalysis
Dimensionless
A substance that has little catalytic activity itself but greatly increases the effectiveness of a catalyst.
Protein
Biochemistry & Polymer Chemistry
g/mol
A large biomolecule made of one or more chains of amino acids folded into a specific three-dimensional shape.
Proton
Atomic Structure & Periodicity
u
A positively charged subatomic particle found in the atomic nucleus, carrying a charge of +1 elementary unit.
m_p = 1.6726 × 10⁻²⁷ kg
Proton Affinity
Acids, Bases & Salts
kJ/mol
The energy released when a gaseous species accepts a proton, measuring intrinsic basicity free of solvent effects.
B(g) + H⁺(g) → BH⁺(g)
Pseudo-First-Order Reaction
Chemical Kinetics & Catalysis
s⁻¹
A higher-order reaction that behaves as first order because one reactant is present in such large excess that its concentration is effectively constant.
rate = k′[A], k′ = k[B]₀
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.
Purity
Foundations of Chemistry
Dimensionless
The mass fraction of the desired substance in a sample, usually expressed as a percentage of the total mass.
purity % = (mass of pure substance / total mass) × 100
Pyrolysis
Stoichiometry & Chemical Reactions
°C
The thermal decomposition of a substance at high temperature in the absence of oxygen.
complex → simpler fragments (Δ, no O₂)
Qualitative Analysis
Analytical Chemistry & Spectroscopy
Dimensionless
Analysis carried out to establish which species are present in a sample.
Quantitative Analysis
Analytical Chemistry & Spectroscopy
Various
Analysis carried out to determine the amount or concentration of a species in a sample.
Quantum Mechanical Model
Atomic Structure & Periodicity
Dimensionless
The modern description of the atom in which electrons are represented by wavefunctions giving probability distributions rather than definite paths.
Ĥψ = Eψ
Quaternary Structure
Biochemistry & Polymer Chemistry
Dimensionless
The arrangement of two or more folded polypeptide chains into a functional protein complex.
Racemic Mixture
Organic Chemistry
degrees
An equimolar mixture of two enantiomers, which shows no net optical rotation.
50:50 (+) and (−)
Radiation Dose
Nuclear & Radiochemistry
Gy
A measure of the energy deposited in matter by ionising radiation.
D = E / m
Radioactive Activity
Nuclear & Radiochemistry
Bq
The number of nuclear disintegrations occurring in a sample per unit time.
A = λN
Radioactive Decay Series
Nuclear & Radiochemistry
Dimensionless
A sequence of successive radioactive decays leading from a long-lived parent to a stable end product.
Radioactive Half-Life
Nuclear & Radiochemistry
s
The time required for half the nuclei in a radioactive sample to decay.
t½ = 0.693 / λ
Radioactive Tracer
Nuclear & Radiochemistry
Bq
A radioisotope introduced into a system so that its pathway can be followed by detecting its radiation.
Radioactive Waste
Nuclear & Radiochemistry
Bq/kg
Material containing radionuclides for which no further use is foreseen and which requires controlled disposal.
Radioactivity
Nuclear & Radiochemistry
Bq
The spontaneous emission of particles or electromagnetic radiation from unstable atomic nuclei.
Radiocarbon Dating
Nuclear & Radiochemistry
years
A dating technique that determines the age of organic material from its residual carbon-14 content.
t = (t½ / 0.693) ln(N₀/N)
Radioisotope
Nuclear & Radiochemistry
Dimensionless
An isotope of an element whose nucleus is unstable and undergoes radioactive decay.
Radiolysis
Nuclear & Radiochemistry
Dimensionless
The chemical decomposition of a substance caused by ionising radiation.
H₂O →(radiation) H· + OH·