OCR A A level Chemistry Definitions

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  • Created by: Ruhab21
  • Created on: 29-09-20 01:59
Define isotopes
Isotopes are atoms of the same element with different numbers of neutrons and different masses
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Define relative atomic mass.
The relative atomic mass for an element is the weighted mean mass of an atom of an element relative to the 1/12th mass of an atom of carbon-12,
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Define relative isotopic mass
The mass of one isotope relative to 1/12th of the mass of a carbon-12 atom
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Define mole
The amount of substance which contains as many elementary particles as there are atoms in exactly 12g of carbon-12.
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Define molar mass
The mass of one mole of substance
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Define molar gas volume
The volume per mole of gas molecules at a stated temperature and pressure
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Define Lowry-Bronsted acid
Proton donor
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Define alkali
A substance which releases -OH in solution
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Define Lowry-Bronsted base
Proton acceptor
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Define salt
A salt is produced when the H+ ion of an acid is replaced by a specific metal ion or NH4+.
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Define orbital
A region of space that can hold up to two electrons
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Define first ionisation energy
The energy required to remove one mole of an electron from each atom in one mole of gaseous atoms to make one mole of gaseous single charged ions.
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Define second ionisation energy
The energy required to remove one electron from each single charged ion in one mole of gaseous single charged ions to make one mole of gaseous single charged ions.
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Define covalent bond
The electrostatic attraction between a positively charged nucleus and a shared pair of electrons.
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Define dative covalent bond
A covalent bond where only one of the bonded atoms donates both electrons being shared
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Define electronegativity
The ability of an atom to attract a bonding pair of electrons
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Define hydrogen bonding
The interaction between the lone pair of electrons on a nitrogen, oxygen and fluorine atom and a hydrogen atom which is bonded to an N, O or F atom.
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Define ionic bond
The electrostatic attraction between oppositely charged ions
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Define metallic bond
The electrostatic attraction between positively charged metal ions and delocalised electrons
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Define periodicity
The repeating pattern of properties of elements across different periods in the Periodic Table
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Define disproportionation
When an element is being both oxidised and reduced in a redox reaction
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Define the rate of reaction
The change in concentration of reactant or product per unit time
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Define Le Chatelier's Principle
When a system under dynamic equilibrium is subjected to a change, the equilibrium will shift so as to oppose the change
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Define standard conditions
Temperature= 298K. Pressure= 101kPa. Solution concentration= 1moldm^(-3). All substances in their standard states
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Define standard enthalpy of formation
The enthalphy change when 1 mole of a compound is forned in its standard state from its constituent element in their standard states, under standard conditions
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Define standard enthalpy of combustion
The enthalpy change when 1 mole of a substance in its standard state reacts completely with oxygen under standard conditions
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Define standard enthalphy change of neutralisation
When 1 mole of water is created by the neutralisation of an acid with an alkali under standard conditions
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Define homologous series
A family of organic compounds with the same functional group but with each successive member differently bu CH2.
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Define structural isomer
Have the same molcular formula but a different structural formula
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Define homolytic fission
Where the covalent bond breaks equally so each product recieves one of the shared pair of electrons to form radicals
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Define heterolytic fission
Where the covalent bond breaks unequally so one product gets both the electrons from the shared pair and the other gets nothing, producing ions.
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Define radical
A species with an unpaired electron
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Define nucleophile
Electron pair donor
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Define electrophile
Electron pair acceptor
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Define sigma bond
Sigma bonds are formed by the direct overlap of orbitals directly between the bonding atoms
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Define stereoisomerism
Compounds with the same structural formula but with a different spatial arrangement of atoms
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Define IR spectroscopy
Its used to identify which functional groups are present in a given molecule
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Define fingerprint region
The fingerprint region is unique to a particular molecule and is used to identify known substances from a database
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Define half life
The time taken for the concentration of one reactant to fall by half original value
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Define rate determining step
The slowest step in the reaction mechanism of a multistep reaction which determines the overall rate
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Define partial pressure
The pressure exerted if one gas in a mixture occupied the whole container alone
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Define Ka
The extent of the dissociation of an acid or [H+][A-]/ [HA]
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Define buffer
A solution that resists changes in pH when small amounts of acid or alkali are added
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Define standard potential electrode
The voltage measured when the named electrode is connected to the standard hydrogen electrode at 298K; under 100kPa with solutions of 1.00moldm^(-3)
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Define fuel cell
A fuel cell uses the energy generated from the reaction between a fuel and oxygen to create a voltage
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Define transition metal
A d-block element that forms one or more stable ions with incompletely filled d-orbitals
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Define complex
A complex consists of a central metal ion/metal surrounded by ligands which are bonded coordinately
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Define ligand
A molecule or an ion which donates a lone pair of electrons to the transition metal by coordinate bonding
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Define coordination number
The number of coordinate bonds in the complex
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Define bidentate
Some ligands can donate two pairs of electrons, to make two coordinate bonds
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Define arenes
Compounds which contain unsaturated rings with delocalised electrons within the ring
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Define chiral centre
A carbon with four different groups/atoms attached to it
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Define condensation polymerisation
The joining of bifunctional monomers with the elimination of a small molecule such as water or HCl.
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Define lattice enthalpy
The energy released when 1 mole of solid crystals are formed from the constituent ions in the gaseous state under standard conditions of 298K and 101kPa
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Define atomisation of metal/non-metal
The energy change when 1 mole of gaseous atoms are formed from the element in its standard state
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Define first ionisation of metal
The energy change when each atom in 1 mole of gaseous atoms loses 1 electron to become 1 mole of gaseous unipositive ions
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Define electron affinity
The energy change when 1 mole of atoms gain 1 mole of electrons in the gaseous state
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Define enthalpy of hydration
the energy change when 1 mole of gaseous ions are completely hydrated by water
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Define enthalpy of solution
The energy change when 1 mole of a solute is dissolved in water under infinite dilution
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Other cards in this set

Card 2

Front

Define relative atomic mass.

Back

The relative atomic mass for an element is the weighted mean mass of an atom of an element relative to the 1/12th mass of an atom of carbon-12,

Card 3

Front

Define relative isotopic mass

Back

Preview of the front of card 3

Card 4

Front

Define mole

Back

Preview of the front of card 4

Card 5

Front

Define molar mass

Back

Preview of the front of card 5
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