A level Definitions Flashcards Preview

Chemistry A-Level James > A level Definitions > Flashcards

Flashcards in A level Definitions Deck (53):
1

Relative Isotopic Mass

The mass of an atom of an isotope compared with 1/12th mass of carbon-12

2

Relative Atomic Mass (Ar)

The weighted mean mass of an atom of an element compared with 1/12th mass of carbon-12

3

Isotopes

Atoms of an element with the same number of protons but different number of neutrons.

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Molar Mass

Mass per mole units g mol^-1

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Mole

The amount of substance 1 mole is 6.02 x 10^23 particles

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Acid

Releases H+ ion aqueous solution

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Alkali

A soluble base that releases OH- ions in an aqueous solution.

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Strong Acid

Fully dissociates in solution

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Weak Acid

Partially dissociates in solution

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Orbital

A region around the nucleus that can hold up to two electrons, with opposite spins

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Disproportionation

Oxidation and reduction of the same element

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First Ionisation Energy

The energy needed to remove 1 mole of electrons from 1 mole gaseous of atoms to form one mole of gaseous 1+ ions.

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Ionic bonding

The electrostatic attraction between oppositely charged ions. (usually between a metal and non-metal)

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Covalent Bonding

Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms ( 2 non-metals)

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Polar molecule

Compound has polar bonds with dipoles that do not cancel due to their direction

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Metallic bonding

The electrostatic attraction between positively charged metal ions and the sea of delocalised electrons.

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Electronegativity

the ability of an atom to attract the bonding electrons in a covalent bond

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Standard states

physical states under standard conditions

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Standard conditions

Temperature: 298 kelvin Pressure: 100 KPa

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Enthalpy change of formation

The enthalpy change when one mole of a compound is formed from its elements in their standard states

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Enthalpy change of combustion

The enthalpy change for the complete combustion of one mole of a substance

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Enthalpy change of neutralisation

The enthalpy change for the formation of 1 mol of water from a neutralisation reaction

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Activation energy

the minimum energy required for a reaction to take place

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Homologous Series

(a series of organic compounds having) the same functional group but with each successive member differing by CH2

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Structural isomers

Compounds with the same molecular formula but different structural formula

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Homolytic fission

Breaking a covalent bond to form two radicals

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Heterolytic fission

Breaking a covalent bond to form two oppositely charged ions

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E/Z isomerism

an example of stereoisomerism, due to restricted rotation about a double bond and two different groups attached to each carbon atom of the C=C group

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Cis-trans isomerism

A special case of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same

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Electrophile

An electron pair acceptor

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Nucleophile

An electron pair donor

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Homogeneous catalyst

A catalyst in the same state as the reactants (usually in solutions)

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Heterogeneous catalyst

- A catalyst in a different state to the reactants (usually a solid catalyst with reactants in solution or gas)

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Dynamic equilibrium

When the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of reactants and products do not change in a closed system

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Catalyst

Chemical that increases the rate of both forward and reverse reactions in an equilibrium by the same amount resulting in an unchanged position of equilibrium

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σ-bond

Overlap of orbitals directly between the bonding atoms

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π-bond

Sideways overlap of adjacent p-orbitals above and below the bonding C atoms

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Stereoisomerism

Compounds with the same structural formula but a different arrangement of atoms in space

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Curly arrow

Shows the movement of an electron pair during a reaction

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Rate of reaction

the rate at which the concentration of a reactant or product is formed/used

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Half-life

The time taken for the concentration of a reactant to half

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Rate-determining step

the slowest step in a multistep reaction

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Brønsted-Lowry acid

a species that donates a proton (H+)

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Brønsted-Lowry base

a species that accepts a proton (H+)

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Buffer solution

a system that minimises pH changes on addition of small amounts of an acid or a base

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Lattice Enthalpy

enthalpy change for the formation of 1 mole of ionic lattice from gaseous ions, ΔLEH

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Enthalpy change of solution

enthalpy change for dissolving of 1 mol of solute, ΔsolH

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Enthalpy change of hydration

enthalpy change for dissolving of 1 mol of gaseous ions in water, ΔhydH

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Oxidising agent

the chemical that is reduced and oxidises another species

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Reducing agent

the chemical that is oxidised and reduces another species

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Standard electrode (redox) potential, Eo

the voltage produced when a half cell is connected to a standard hydrogen half-cell, measured at 298K with solution concentrations of 1 mol dm^-3 and a gas pressure of 100KPa.

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Ligand

species that donates a pair of electrons forming a coordinate/dative covalent bond to a metal ion

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Optical isomer

non-superimposable mirror images about a chiral centre