Physical chemistry definitions

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Relative atomic mass
The mass of an atom of an element relative to 1/12th the mass of an atom of carbon-12
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Relative molecular mass
The mass of a molecule relative to 1/12th the mass of an atom of carbon-12
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Empirical formula
The simplest whole number ratio of atoms of each element in a compound
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Molecular formula
The actual number of atoms of each element in a compound
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First ionisation energy
The energy required to remove one electron from each atom in one mole of a gaseous substance
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Electronegativity
The power of an atom to attract electron density towards itself from a covalent bond
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Enthalpy change
The heat energy change measured under conditions of constant pressure
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Standard enthalpy of formation
The enthalpy change when one mole of a substance is formed from its constituent elements in their standard states at standard temperature and pressure
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Standard enthalpy of combustion
The amount of heat energy given out when one mole of a substance is completely burned in oxygen with all reactants and products in their standard states
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Hess' law
The enthalpy change for a chemical reaction is the same whatever route is taken from reactants to products
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Mean bond enthalpy
The average enthalpy change required to break a covalent bond when all species are in a gaseous state
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Activation energy
The minimum energy required to cause a reaction
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Catalyst
A substance that increases rate of reaction by lowering the activation energy, without being changed in chemical composition or amount
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Rate of reaction
The change of concentration of a reactant or product over time
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Le Chatelier's Principle
If a constraint is imposed on a system at equilibrium, the system will respond in such a way as to reduce the effect of the constraint
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Oxidation
The process of electron loss
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Reduction
The process of electron gain
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Oxidising agent
An electron acceptor - a substance that causes the oxidation of another chemical
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Reducing agent
An electron donor - a substance that causes the reduction of another chemical
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Other cards in this set

Card 2

Front

The mass of a molecule relative to 1/12th the mass of an atom of carbon-12

Back

Relative molecular mass

Card 3

Front

The simplest whole number ratio of atoms of each element in a compound

Back

Preview of the back of card 3

Card 4

Front

The actual number of atoms of each element in a compound

Back

Preview of the back of card 4

Card 5

Front

The energy required to remove one electron from each atom in one mole of a gaseous substance

Back

Preview of the back of card 5
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