Chemistry terms starting with E

Enthalpy Thermochemistry & Thermodynamics kJ/mol A thermodynamic state function equal to internal energy plus the product of pressure and volume. H = U + pV

Enthalpy Level Diagram Thermochemistry & Thermodynamics kJ/mol A diagram plotting the enthalpies of reactants and products to show the direction and size of the enthalpy change.

Enthalpy of Atomisation Thermochemistry & Thermodynamics kJ/mol The enthalpy change when one mole of gaseous atoms is produced from an element in its standard state. ΔH_at°

Enthalpy of Dilution Thermochemistry & Thermodynamics kJ/mol The enthalpy change when a solution is diluted from one concentration to another by adding solvent. ΔH_dil

Enthalpy of Fusion Thermochemistry & Thermodynamics kJ/mol The enthalpy change when one mole of a solid melts to a liquid at its melting point. ΔH_fus

Enthalpy of Neutralisation Thermochemistry & Thermodynamics kJ/mol The enthalpy change when an acid and a base react to form one mole of water under standard conditions. H⁺ + OH⁻ → H₂O, ΔH = −57.1 kJ

Enthalpy of Reaction Thermochemistry & Thermodynamics kJ/mol The heat absorbed or released when a reaction occurs at constant pressure in the molar amounts of the balanced equation. ΔH_rxn = ΣΔH_f(products) − ΣΔH_f(reactants)

Enthalpy of Solution Solutions & Colligative Properties kJ/mol The heat absorbed or released when one mole of a substance dissolves completely in a large excess of solvent. ΔH_sol = ΔH_lattice + ΔH_hyd

Enthalpy of Sublimation Thermochemistry & Thermodynamics kJ/mol The enthalpy change when one mole of a solid converts directly into vapour. ΔH_sub = ΔH_fus + ΔH_vap

Enthalpy of Vaporisation Thermochemistry & Thermodynamics kJ/mol The enthalpy change when one mole of a liquid becomes vapour at its boiling point. ΔH_vap

Entropy Thermochemistry & Thermodynamics J/(mol·K) A measure of the dispersal of energy and the number of microscopic arrangements available to a system. S = k ln W

Entropy Change of the Surroundings Thermochemistry & Thermodynamics J/K The entropy change experienced by the surroundings when they absorb or release heat from a system. ΔS_surr = −ΔH_sys / T

Enzyme Biochemistry & Polymer Chemistry Dimensionless A biological catalyst, almost always a protein, that accelerates a specific biochemical reaction.

Enzyme Catalysis Chemical Kinetics & Catalysis Dimensionless Catalysis by protein molecules that bind substrates at a specific active site and lower the activation energy dramatically.

Enzyme Specificity Biochemistry & Polymer Chemistry Dimensionless The ability of an enzyme to select one substrate, or one class of substrate, and catalyse one particular reaction.

Equilibrium Constant Chemical Equilibrium Various The fixed ratio of product to reactant terms, each raised to its stoichiometric power, that characterises a reaction at a given temperature. K = Π[products]^ν / Π[reactants]^ν

Equilibrium Constant of a Reversed Reaction Chemical Equilibrium Various The constant obtained when a reaction is written in the opposite direction, equal to the reciprocal of the original. K_reverse = 1 / K_forward

Equilibrium Constant of a Scaled Reaction Chemical Equilibrium Various The constant obtained when every coefficient in an equation is multiplied by the same factor. K_new = K_old^n

Equilibrium in Closed Systems Chemical Equilibrium Dimensionless The requirement that no matter enters or leaves for a true chemical equilibrium to be established.

Equilibrium Position Chemical Equilibrium mol/L The particular set of concentrations at which a system settles, describing how far the reaction has proceeded.

Equilibrium Yield Chemical Equilibrium Dimensionless The proportion of reactant converted to product once equilibrium has been reached. yield = n_product / n_theoretical

Equivalence Point Acids, Bases & Salts mol The point in a titration at which exactly stoichiometric amounts of the two reactants have been combined. n_acid × basicity = n_base × acidity

Equivalent Weight Stoichiometry & Chemical Reactions g/equiv The mass of a substance that combines with or displaces 1.008 g of hydrogen, 8 g of oxygen or one mole of electrons. E = M / n-factor

Ester Organic Chemistry Dimensionless A compound formed by replacing the acidic hydrogen of a carboxylic acid with an alkyl group. R–COO–R′

Terms starting with E