60 terms

IB chemistry definitions

All required ib definitions
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Exothermic reaction
Gives off heat, negative enthalpy and is involved with forming bonds (Bonds in products stronger than those in reactants)
Endothermic reaction
absorbs heat, positive enthalpy and is involved with breaking bonds (Bonds in reactants stronger than those in products)
Bond, π: Pi bond
A radial bond formed by the sideways overlap of p orbitals with e- densities concentrated above and below a line drawn through the two nuclei. Double bonds have one π bond, while triple bonds have two which are perpendicular to each other
Bond, σ: Sigma bond
An axial bond formed by the head on/head-to-head overlap of atomic orbitals from two different atoms along the line drawn through the two nuclei, with e- densities concentrated along the line. Single, double and triple bonds have one σ bond
First ionization energy
Energy require to remove 1 mole of gaseous atoms
Electronegativity
the ability of an atom to attract electrons in a covalent bond
Lewis Acid
Electron pair acceptor
Lewis Base
Electron pair donor
Bronsted-Lowry Acid
Proton donor
Bronsted-Lowry base
Proton acceptor
Strong Acids and Bases
Weak acids and bases
Dissociate completely in solution
Dissociate only partially in solution
Enthalpy change reaction
heat energy transformed under standard conditions
Oxidation
Losing electrons
Reduction
gaining electrons
Buffer solution
solution resistant to changes in pH on the addition of small amounts of acid or alkali.
Acidic buffer
maintains the pH at a value less than 7. made by mixing a weak acid with a salt of weak acid with strong alkali
Basic buffer
maintain the pH at a value greater than 7. made by mixing a weak base and a salt of weak base with strong acid.
Standard electrode potential
the electromotive force (greatest potential difference that a cell can generate) generated when it is connected to the standard hydrogen electrode by an external circuit and a salt bridge. (under standard conditions)
isotopes
atoms with the same atomic number but different mass number (different amount of neutrons)
Molar mass
the molar mass is the mass of one mole of any substance. (g/mol)
Relative atomic mass
average mass of an atom, taking into account the relative abundances of all the naturally occurring isotopes of the element, relative to one atom of C-12.
atomic number
protons in the nucleus (= electrons)
continuous spectrum
shows unbroken sequence of frequencies of light. Such as the spectrum of visible light.
Line spectrum
emission spectrum that has only certain frequencies of light. Produced by excited atoms and ions as they fall back to a lower energy level
Ligand
ion or molecule that donates a pair of electron to a metal atom/ion when forming a coordination complex. They're lewis bases
Electron affinity
energy change occurring when a gaseous atom gains an electron to form a negative ion.
rate of reaction
increase in concentration of products per unit time.
activation energy
minimum energy required for a chemical reaction to take place
Standard electrode potential
electrode potential relative to a hydrogen half-cell measured under standard conditions
Lattice enthalpy
enthalpy change which occurs on the formation of 1 mol of ionic compound from its isolated ions in their gaseous state. (its exothermic)
Standard enthalpy change of reaction
heat transferred during a reation carried out under standard conditions.
Average bond enthalpy
The average bond enthalpy is the energy required to break or form a mole of covalent bonds in the gaseous state.
It is an average value because it takes account of the different energies in a bond between the same atoms in different molecules.
nucleophile
electron-rich species that is attracted to parts of molecules that are electron defficient
Elimination
when a small molecule is removed from a larger molecule, leading to the formation of an unsaturated product.
stereoisomers
differ from each other in the spatial arrangement of their atoms
heterolytic fission
when a bond breaks with both the shared electrons going to one of the products
electrophile
electron deficient species which is attracted to parts of molecules which are electron rich
addition
occurs when two reactants combine to form a single compound
substitution
occurs when one atom or group of atoms in a compound is replaced by a different atom or group
condensation
occurs when two reactants join together and in the process a small molecule is lost. (addition-elimination)
homolytic fission
when a covalent breaks by splitting the shared pair of electrons between the two products
Saturated
Unsaturated
only single bonds
contain double or triple bonds
Racemic Mixture/racemate
Mixture of both Right-Hand and Left Hand enantiomeres
Homogeneous catalyst
A catalyst that is in the same phase as the reactants and products
heterogeneous catalyst
A catalyst that is in a different phase than the reactants and products; it provides a surface on which the reaction can occur.
pH, pOH and pKw
pH =-log10 [H+]
pOH = -log10 [OH-]
pKw = -log10Kw
pKa=-log10Ka
pKb=-log10Kb
pKa + pKb=14
pH=pKa +
Nitrate
Hydrogen carbonate/ bicarbonate

Ammonium
Phosphate
NO3 -
HCO3 -


NH4 +
PO4 3-
Covalent Bond
electrostatic attraction between a pair of electrons and positively charged nuclei.
Metallic Bonding
electrostatic attraction between a lattice of positive ions and delocalized electrons.
Oxides



Chlorides
Oxides: Na2O, MgO, Al2O3, SiO2, P4O6 and P4O10,
SO2 and SO3, Cl2O and Cl2O7

Chlorides: NaCl, MgCl2, Al2Cl6, SiCl4, PCl3 and PCl5,
and Cl2
Solute
A substance that is dissolved into another ( the solvent)
Solvent:
a substance that dissolves another ( the solute)
Mass spectrometer
A device for determining relative atomic masses and their relative abundances. Composed of:
**vaporizer (where the sample is vaporized)
**ionizer (where atoms are bombarded with high energy e- e- knocked off the atoms. Only ions with a +1 charge are formed, in practice),
*accelerator (where an electric field accelerates them), deflector (where a magnetic field deflects them; the smaller the mass and the higher the charge, the greater the deflection) *detector (which measures both the mass and relative amounts of ions present.
Bonds: Van der Walls
Temporary dipole forces due to momentary unevenness in spread of e-. Weakest of intermolecular forces. Increase with increasing molar mass.
Bonds: Dipole-Dipole
Permanent electrostatic forces of attraction between polar molecules. Stronger than van der Waals'.
Bonds: Hydrogen bonding
Occurs when hydrogen is bonded directly to a highly electronegative element (N, F, or O). Stronger than dipole:dipole
forces.
Bonds/Structure Giant covalent
Very hard but brittle. Very high m.p. and b.p. Do not conduct in any state. Insoluble.
Bonds/Structure Giant ionic
Hard but brittle. High m.p. and b.p. Conduct when molten or aqueous, but not as solids.
Bonds/Structure Giant metallic
Malleable, not brittle. M.p. and b.p. dependent on no. of valence e-. Good conductivity.
Bonds/Structure Molecular covalent
Usually soft and malleable unless hydrogen bonded. Low m.p. and b.p. Do not conduct in any state. Often soluble in non-aqueous solvents, unless they can hydrogen bond to water.
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