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960 terms · page 12 of 40


A–Z
All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Foundations of Chemistry

Distillation

A separation technique that exploits differences in volatility by vaporising a liquid and condensing the vapour in a separate vessel.

Dimensionless
Chemical Equilibrium

Distribution Law

The principle that a solute distributes itself between two immiscible solvents in a constant ratio at fixed temperature.

K_D = C_organic / C_aqueous Dimensionless
Biochemistry & Polymer Chemistry

DNA

The double-stranded nucleic acid that carries the hereditary information of almost all living organisms.

Dimensionless
Stoichiometry & Chemical Reactions

Double Displacement Reaction

A reaction in which two compounds exchange partner ions to form two new compounds.

AB + CD → AD + CB Dimensionless
Biochemistry & Polymer Chemistry

Double Helix

The structure of DNA, in which two antiparallel polynucleotide strands wind around a common axis.

10.5 base pairs per turn nm
Acids, Bases & Salts

Double Salt

A salt containing two different cations or anions that dissociates completely into all its constituent ions in solution.

e.g. K₂SO₄·Al₂(SO₄)₃·24H₂O Dimensionless
Electrochemistry & Redox

Dry Cell

A primary cell using a moist paste rather than a liquid electrolyte, so it can be used in any orientation.

Zn + 2MnO₂ + 2NH₄⁺ → Zn²⁺ + Mn₂O₃ + 2NH₃ + H₂O V
Chemical Equilibrium

Dynamic Equilibrium

An equilibrium in which opposing processes continue at the molecular level but at equal and opposite rates.

rate_forward = rate_reverse Dimensionless
Inorganic & Coordination Chemistry

d–d Transition

The promotion of an electron between split d orbitals, responsible for the characteristic colours of transition metal complexes.

ΔE = hν = Δ nm
Organic Chemistry

E1 Reaction

A two-step elimination proceeding through a carbocation, which then loses a proton to form an alkene.

rate = k[substrate] s⁻¹
Organic Chemistry

E2 Reaction

A single-step elimination in which a base removes a proton as the leaving group departs, forming a double bond.

rate = k[substrate][base] L/(mol·s)
Solutions & Colligative Properties

Ebullioscopic Constant

The boiling point elevation produced by a one-molal solution of a non-electrolyte in a given solvent.

K_b = RT_b²M / ΔH_vap K·kg/mol
Chemical Equilibrium

Effect of a Catalyst on Equilibrium

A catalyst changes how quickly equilibrium is reached but never where that equilibrium lies.

K unchanged Dimensionless
Chemical Equilibrium

Effect of an Inert Gas

The influence of adding a non-reacting gas on the position of a gaseous equilibrium.

Pa
Chemical Equilibrium

Effect of Concentration Change

The shift in equilibrium position caused by adding or removing a reactant or product.

Q ≠ K → shift until Q = K mol/L
Chemical Equilibrium

Effect of Pressure Change

The shift in a gaseous equilibrium caused by changing the total pressure through a volume change.

shift towards fewer gas moles when p rises Pa
Chemical Equilibrium

Effect of Temperature Change

The shift in equilibrium caused by heating or cooling, which uniquely also changes the equilibrium constant.

exothermic: K falls as T rises K
Inorganic & Coordination Chemistry

Effective Atomic Number Rule

The observation that stable metal carbonyls tend to have a total electron count equal to that of the next noble gas.

EAN = Z − oxidation state + 2n(ligands) Dimensionless
Chemical Kinetics & Catalysis

Effective Collision

A collision that actually leads to reaction because it has both sufficient energy and correct orientation.

Dimensionless
Atomic Structure & Periodicity

Effective Nuclear Charge

The net positive charge actually experienced by a particular electron after allowing for shielding by other electrons.

Z_eff = Z − σ Dimensionless
Stoichiometry & Chemical Reactions

Effervescence

The rapid escape of gas bubbles from a liquid during a chemical reaction.

Dimensionless
States of Matter & Gas Laws

Effusion

The escape of gas molecules one at a time through a hole much smaller than the mean free path.

rate ∝ 1 / √M mol/s
Electrochemistry & Redox

Electrochemical Cell

A device in which a redox reaction and an electric current are interconverted through two separated electrodes.

V
Electrochemistry & Redox

Electrochemical Equivalent

The mass of a substance liberated by the passage of one coulomb of charge.

Z = M / (nF) g/C