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960 terms · page 12 of 40
Distillation
Foundations of Chemistry
Dimensionless
A separation technique that exploits differences in volatility by vaporising a liquid and condensing the vapour in a separate vessel.
Distribution Law
Chemical Equilibrium
Dimensionless
The principle that a solute distributes itself between two immiscible solvents in a constant ratio at fixed temperature.
K_D = C_organic / C_aqueous
DNA
Biochemistry & Polymer Chemistry
Dimensionless
The double-stranded nucleic acid that carries the hereditary information of almost all living organisms.
Double Displacement Reaction
Stoichiometry & Chemical Reactions
Dimensionless
A reaction in which two compounds exchange partner ions to form two new compounds.
AB + CD → AD + CB
Double Helix
Biochemistry & Polymer Chemistry
nm
The structure of DNA, in which two antiparallel polynucleotide strands wind around a common axis.
10.5 base pairs per turn
Double Salt
Acids, Bases & Salts
Dimensionless
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
Dry Cell
Electrochemistry & Redox
V
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
Dynamic Equilibrium
Chemical Equilibrium
Dimensionless
An equilibrium in which opposing processes continue at the molecular level but at equal and opposite rates.
rate_forward = rate_reverse
d–d Transition
Inorganic & Coordination Chemistry
nm
The promotion of an electron between split d orbitals, responsible for the characteristic colours of transition metal complexes.
ΔE = hν = Δ
E1 Reaction
Organic Chemistry
s⁻¹
A two-step elimination proceeding through a carbocation, which then loses a proton to form an alkene.
rate = k[substrate]
E2 Reaction
Organic Chemistry
L/(mol·s)
A single-step elimination in which a base removes a proton as the leaving group departs, forming a double bond.
rate = k[substrate][base]
Ebullioscopic Constant
Solutions & Colligative Properties
K·kg/mol
The boiling point elevation produced by a one-molal solution of a non-electrolyte in a given solvent.
K_b = RT_b²M / ΔH_vap
Effect of a Catalyst on Equilibrium
Chemical Equilibrium
Dimensionless
A catalyst changes how quickly equilibrium is reached but never where that equilibrium lies.
K unchanged
Effect of an Inert Gas
Chemical Equilibrium
Pa
The influence of adding a non-reacting gas on the position of a gaseous equilibrium.
Effect of Concentration Change
Chemical Equilibrium
mol/L
The shift in equilibrium position caused by adding or removing a reactant or product.
Q ≠ K → shift until Q = K
Effect of Pressure Change
Chemical Equilibrium
Pa
The shift in a gaseous equilibrium caused by changing the total pressure through a volume change.
shift towards fewer gas moles when p rises
Effect of Temperature Change
Chemical Equilibrium
K
The shift in equilibrium caused by heating or cooling, which uniquely also changes the equilibrium constant.
exothermic: K falls as T rises
Effective Atomic Number Rule
Inorganic & Coordination Chemistry
Dimensionless
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)
Effective Collision
Chemical Kinetics & Catalysis
Dimensionless
A collision that actually leads to reaction because it has both sufficient energy and correct orientation.
Effective Nuclear Charge
Atomic Structure & Periodicity
Dimensionless
The net positive charge actually experienced by a particular electron after allowing for shielding by other electrons.
Z_eff = Z − σ
Effervescence
Stoichiometry & Chemical Reactions
Dimensionless
The rapid escape of gas bubbles from a liquid during a chemical reaction.
Effusion
States of Matter & Gas Laws
mol/s
The escape of gas molecules one at a time through a hole much smaller than the mean free path.
rate ∝ 1 / √M
Electrochemical Cell
Electrochemistry & Redox
V
A device in which a redox reaction and an electric current are interconverted through two separated electrodes.
Electrochemical Equivalent
Electrochemistry & Redox
g/C
The mass of a substance liberated by the passage of one coulomb of charge.
Z = M / (nF)