Ib Chemistry Definitions (Hl)

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ligand

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Neutral molecule or anion which contains a non-bonding pair of electrons. They can form coordinate covalent bonds with a metal ion to form complex ions.

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standard enthalpy change of formation

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The enthalpy change on the formation of one mole of a compound from its elements in their standard states at 298 K and 1 atm pressure

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standard enthalpy of atomization

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The standard enthalpy change when one mole of gaseous atoms is formed from the element in its standard state under standard conditions

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electron affinity

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The enthalpy change when an electron is added to an isolated atom in the gaseous state (usually exothermic)

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lattice enthalpy

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The endothermic process of turning a crystalline solid into its gaseous ions or the exothermic process of turning gaseous ions into a crystalline solid

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buffer solution

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A solution that maintains a relatively constant pH when small amounts of strong acid or strong base are added to it

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heterogeneous catalyst

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A catalyst that is in a different phase than the reactants and products; it provides a surface on which the reaction can occur.

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homogeneous catalyst

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A catalyst that is in the same phase as the reactants and products

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standard electrode potential

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The potential of a half cell to lose or gain electrons as compared to the standard hydrogen electrode, which is assigned a value of 0 V.

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standard hydrogen electrode

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Assigned a value of 0 V under standard conditions of 1 atm pressure, 298 K, and 1.0 mol/dm^3 hydrogen ion concentration

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structural isomers

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Compounds that have the same molecular formula but a different structural formula

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unsaturated

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Containing at least one carbon=carbon double bond

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saturated

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Containing no carbon=carbon double bonds

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nucleophile

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Reagents that have a non-bonding pair of electrons; attracted to the carbon atom in halogenoalkanes during substitution reactions

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geometric isomerism

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Isomerism that occurs when rotation about a bond is restricted or prevented (usually occurs with asymmetric non-cyclic alkenes)

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optical isomerism

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Isomerism that occurs in all compounds containing at least one chiral carbon (nonsuperimposable mirror images)

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enantiomers

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Optical isomers; nonsuperimposable mirror images

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racemic mixture

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A mixture in which two enantiomers are present in equal amounts

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chiral carbon

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A carbon atom that contains four different groups or atoms bonded to it

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precision

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How close several experimental measurements of the same quantity are to each other

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accuracy

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How close the readings are to the true value

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Standard state of an element or compound

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its most stable state under the specified conditions.

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Standard enthalpy change of combustion

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the enthalpy change on the complete combustion of one mole of the compound in its standard state in excess oxygen under standard conditions

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Rate Constant (k)

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the constant in the rate equation:

Rate = k[A]^m [B]^n

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Order of reaction

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with respect to a reactant: the powered to which its concentration is raised in the rate equation
overall: sum of the orders with respect to the individual reactants

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pH, pOH and pKw

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pH =-log10 [H+]
pOH = -log10 [OH-]
pKw = -log10Kw