Chemistry Terms- Leaving Cert Higher Level Chemistry

Leaving CertificateChemistry

Heat of Combustion – The heat produced when one mole of a substance is completely burnt in excess oxygen.

Heat of Formation – The heat change when one mole of a compound in its standard phase is formed from each of its elements in their standard phases.

Heat of Reaction – The heat change when the numbers of moles indicated in the balanced equation for the reaction reacts completely.

Heat of Neutralization – The heat change when one mole of H+ ions from an acid reacts with one mole of OH- ions from a base.

Hess’s Law of Heat Summation – The heat change for a reaction is the same whether the reaction takes place in one step or several steps.

Law of Lavoisier and Laplace – Heat change for reverse reaction is equal but opposite in sign to forward reaction

Exothermic – Gives out heat. Feels hot. ∆H is negative

Endothermic – Takes in heat. Feels cold. ∆H is positive

Atom – Smallest particle of matter that can exist by itself

Matter – Anything that occupies space

Element – Substance made up of one type of atom – cant be broken into anything simpler by chemical means

Molecule – Smallest particle of substance that shows properties of that substance Group of atoms chemically joined

Solution – Mixture of solute [solid] and solvent [liquid]. Cannot be separated by filtration.

Mixture – Two or more substances not chemically joined. Composition can vary.

Isotopes – Forms of element with different mass number due to different numbers of neutrons

The Mole – 1 mole = 1 mole= RMM (relative molecular mass) in grams = Avogadro’s number (6*1023)= 22.4l of any gas at STP [ 273 K and 760mm of Hg ]

Avogadro’s Law – 1 mole of any gas at STP occupies 22.4 L

Kinetic Energy – = ½ mv2 [m = mass, v = velocity]

Atomic Number – Number of protons in an atom. Determines what the element is.

Mass number – Number of Protons + neutrons in an atom

Relative Atomic Mass – 1. average of the mass numbers of the isotopes of the element. 2. as they occur naturally 3. taking their abundances into account4. expressed on a scale on which atoms of the carbon 12 isotope have a mass of exactly 12 units.

Relative Molecular Mass – 1. The sum of the relative atomic masses of all the atoms in a molecule of the compound.2. The mass of one molecule of that compound compared with one twelfth of the mass of the carbon 12 isotope.3. Mass of one mole of a compound = Relative Molecular Mass in grams.

Energy Level – The fixed energy value that an electron in an atom may have.

Atomic Orbital – The region in space within which there is a high probability of finding an electron.

Hund’s Rule of Maximum Multiplicity – When 2 or more orbitals of equal energy are available, the electrons occupy them singularly before filling them in pairs.

Aufbau Principle – Electrons occupy the lowest available energy level.

Pauli Exclusion Principle – No more than 2 electrons may occupy an orbital and they must have opposite spin.

Heisenberg’s Uncertainty Principle – The more accurately we know the position of a particle the less accurately we know its velocity.

First Ionisation Energy – The energy required to completely remove the most loosely bound electron from a neutral gaseous atom in its Ground State. [ X – e- = X+ ]

Second Ionisation Energy – The energy required to completely remove the second most loosely bound electron from the ion X+ – e- = X2+

Atomic Radius – Half the distance between 2 adjacent atoms of the same element joined by a single covalent bond

Oxidation Number – The charge that an atom has or appears to have when electrons are distributed according to certain arbitrary rules.

Electronegativity – The relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond.

Boyle’s Law – At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure.

Charles’s Law – At constant pressure, the volume of a fixed mass of gas is directly proportional to its temperature measured on the Kelvin scale.

Equation of State [for an ideal gas] – PV = nRT [ n = number of moles, V=volume in m3; T = Kelvin; R = gas constant 8.31; p = pressure]

Avogadro’s Law – Equal volumes of gases contain equal numbers of molecules, under the same conditions of temperature and pressure.

EDTA – Ethylenediaminetetraacetic acid

Acid – Arrhenius: a substance that dissociates in water to produce H+ ions.Bronsted-Lowry a proton [H+] donor.

pH : -log10[H+] or -log10[H3O+] = 14 – pOH = -log10√(Ka * [H3O+])

Base – Arrhenius: a substance that dissociates in water to produce OH- ions.Bronstead-Lowry:a proton [H+] acceptor.

Amphoteric – Has both acid and basic properties at the same time. E.g. Aluminium, aluminium oxide

pOH : -log10[OH-]

Radioactivity – The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation.

Half-life – The time taken for half of the nuclei in any given sample to decay.

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