IB Definitions
CORE
Define the terms relative atomic mass
(Ar) and relative molecular mass (Mr).relative atomic mass
weighted mean mass of all the naturally occuring isotopes of an
element relative to the mass of an atom of 12Crelative molecular
mass average mass of the molecules in a sample of pure substance
relative to the mass of an atom of carbon 12
Define the terms first ionization energy
and electronegativity.
The first ionization energy minimum energy required to remove
the outermost electron from each atom in a mole of gaseous
atomsElectronegativity measure of the ability of an atom to attract
a pair of electrons in a covalent bond
The standard enthalpy change of a reaction is the enthalpy
change when one mole of reactants is transformed into products at
298K and 101.3 KPa (1atm)
The average bond enthalpy is the average energy change when 1
mole of a particular covalent bond is broken to give atoms;
reactants and products being in the gaseous state.e.g. HCl (g)
--> H(g) + Cl(g)
The rate of a chemical reaction is the rate of disappearance of
reactants or the rate of appearance of products. (can be a rate of
concentration change, pressure change, volume change)
N.B. colour change is an indirect measurement of concentration
changeActivation energy (Ea) is the minimum energy required for a
chemical reaction to occurOxidising agent is a substance which will
usually easily remove electrons from other substances in a redox
reaction (eg halogens, O2, Ag+ --> Ag(s) ).
Reducing agent is a substance which will usually easily lose
electrons to other substances in a redox reaction (eg Al in: 2Al(s)
+ Fe2O3 (s) ---> 2Al2O3 + 2Fe HL
A ligand is an molecule or ion capable of donating a pair of
electrons to a central metal atom or ion
Standard stateis the accepted form of the substance at 298K and
101.3KPa (1atm) (eg graphite for carbon and not diamond, O2 for
oxygen and not O3)
Standard enthalpy change of formation is the enthalpy change
when one mole of a substance is formed from its elements in their
standard states. Reactants and products at 298K and 101.3 Kpa (1
atm)e.g. Hfo C(graphite) =0 KJ mol-1, Hfo S8 = 0 KJ mol-1, Hfo SO2
= -296.84 KJ mol-1
Standard enthalpy change of combustion is the enthalpy change
when one mole of a substance is completely burned in oxygen.
Reactants and products at 298K and 101.3 Kpa (1 atm)
S(s) + O2 (g) --> SO2(g)
Hco = -296.84 KJ mol-1
N.B. for reactions of elements with oxygen Hco equals HfoDefine
and apply the terms lattice
enthalpy and electron affinity.
The lattice enthalpy is the energy evolved when one mole of an
ionic compound is formed from gaseous ions under standard
conditionsElectron affinity is the energy change that occurs when
an electron is added to a gaseous atom or ion
Define the term standard electrode
potential (Eo )The standard electrode potential is the potential
of a half cell compared to the standard hydrogen electrode (SHE) at
298K and 101.3 KPa (1atm). All solutions at a concentration of
1MStereoisomerism same struct. Form, diff arrange. in space.
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