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Thermodynamics, Enthalpy and Entropy (Definitions (Spontaneous (The…
Thermodynamics, Enthalpy and Entropy
Definitions
Spontaneous
The reaction continuous after the activation energy has been supplied with no further input of energy needed.
Disordered state
e.g. water/gas, dissolved ionic lattice in water, you after a car accident :
Ordered state
e.g. solid, ionic lattice, you
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Change in entropy
From order -> disorder is an increase - reaction will be spontaneous even if it is endothermic. From disorder -> order is a decrease, won't happen unless energy is donated
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Non-Spontaneous
The reaction needs energy to be constantly supplied for it to occur, you have to start the reaction and start the reaction and start the reaction over and over again, an example of this would be photosynthesis as this needs energy constantly supplied via respiration
Enthalpy of formation
The enthalpy change when one mole of a compound is formed from its constituent parts at standard conditions
Enthalpy of combustion
The enthalpy change when one mole of a substance is completely burned in oxygen at standard conditions
Enthalpy of atomisation
The enthalpy change when one mole of gaseous atoms are formed from the element in its standard state.
First ionisation energy
The enthalpy required to remove one mole of electrons from one mole of gaseous ions at standard conditions.
Second ionisation energy
The enthalpy required to remove one mole of electrons from one mole of gaseous ions, which have already lost an electron, at standard conditions.
First electron affinity
The enthalpy change when a mole of gaseous atoms is converted to a mole of gaseous ions, via the addition of one mole of electrons, so that each of the ions has a single negative charge. This is at standard conditions.
Second electron affinity
The enthalpy change when a mole of gaseous ions, each with a single negative charge, is converted to a mole of gaseous ions, each with a double negative charge, via the addition of one mole of electrons.This is at standard conditions.
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Enthalpy of solution
The enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which molecules or ions are far enough apart to not interact with each other.
Mean bond enthalpy
The enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds
Boiling water experiment
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220,000/2.5 = 88,000Jmol^-1
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Entropy
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How disordered something is. Measured by how much energy is required to push a system towards disorder.
Gibbs free energy change
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DON'T FORGET THAT ENTROPY IS IN J MOL^-1 K^-1 AND ENTHALPY IS IN KJ MOL^-1 SO NEED TO CONVERT BETWEEN THEM