ENTHALPY AND ENTROPY
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- Created by: Jalal12362
- Created on: 20-03-18 21:52
Define lattice enthalpy
Enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.
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Is lattice enthalpy exothermic or endothermic
Exothermic
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Describe route 1 of lattice enthalpy determination (1)
1) Changing elements to gaseous atoms from their standard states. This is endothermic
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Describe route 1 of lattice enthalpy determination (2)
Then change it to gaseous ions.
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Describe route 1 of lattice enthalpy determination (3)
Now you must change gaseous ions to solid ionic lattices. This is the lattice enthalpy and is exothermic.
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What is route 2 of forming ionic compound?
Directly turning elements from their standard states to the ionic compound. Enthalpy of formation.
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What is the standard enthalpy of formation?
Enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactant and products in their standard states.
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What is enthalpy of change atomisation?
Enthalpy change that takes place for the fformation of one molre of gaseous atoms from the element in its standard conditions.
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Is lattice enthalpy of atomisation endothermic or exothermic, and why?
Endothermic, because bonds are broken to form gaseous atoms.
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What is the first ionisation energy?
Enthalpy change to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
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What is the first electron affinity?
Enthalpy change that takes place when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1-ions
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What is the enthalpy change of solution?
Enthalpy change that takes place when one mole of a solute dissolves in a solvent.
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Describe the bonding in aqueous NaCl?
In the aqueous ions, the delta positive and delta negative charges in the water molecules are attracted towards the positive and negative ions. The partially negative oxygen atom is attracted to the positive sodium ion.
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Describe the bonding in aqueous NaCl? (2)
The partially positive hydrogen atoms is attracted to the negative chloride ion.
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What is lattice enthalpy of hydration?
Enthalpy change when gaseous ions dissolve in water to form one mole of aqueous ions.
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Describe the effect of Ionic charge on lattice enthalpy
A higher ionic charge results in both lattice enthalpy and enthalpy of hydration being more exothermic. This is due to stronger electrstatic attractions
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What is the effect of ionic radius?
Smaller ionic radius results in both lattice enthalpy and enthalpy of hydration being more exothermic, the is because the smaller radius gives greater charge density, resulting in stronger electrostatic attractions
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Explain the effect of ionic size on lattice enthalpy of a metal.
Ionic radius increases, attraction between ions decreases, lattice energy less negative, melting point decreases.
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What is entropy?
It is the measure of the number of ways that energy can be shared out in a system, or the number of ways that particles can be arranged.
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Systems that are more chaotic have ........ entropy
higer
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Most entropy______________Lowest entropy
Solid----> Liquid-----> Gas
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What is the equation for standard entropy?
Entropy change = (sum of products entropy) - (sum of entropy of reactants)
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What is the feasibility of a reaction?
If it can occur sponaneously or not. Reactions are feasible when delta G is negative or zero.
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What is the Gibbs Free energy equation?
Delta G = (enthalpy change) - (entropy change) ( temp in kelvin K)
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Enropy increases when............
particles change state from solid ---> Liquid ----> Gas. When solid dissolves, the number of particles increases
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Problems with the predictions of entropy?
Reactions maybe very slow or activation energy is too high, even though the reaction is feasible.
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Other cards in this set
Card 2
Front
Is lattice enthalpy exothermic or endothermic
Back
Exothermic
Card 3
Front
Describe route 1 of lattice enthalpy determination (1)
Back
Card 4
Front
Describe route 1 of lattice enthalpy determination (2)
Back
Card 5
Front
Describe route 1 of lattice enthalpy determination (3)
Back
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