Chemistry UNIT 5 Enthalpy & Entropy

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  • Created by: JessAnnB
  • Created on: 31-03-16 15:01
What is the enthalpy of formation?
Enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions.
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What is the first ionisation enthalpy?
The energy required to remove one electron from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+.
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What is enthalpy of atomisation of an element?
The enthalpy change when one mole of free gaseous atoms is produced from that element in its standard state.
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What is first electron affinity?
The energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous 1- ions.
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What is bond dissociation enthalpy?
The mean enthalpy change when one mole of covalent bonds is broken homolytically, resulting in free gaseous atoms.
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What is Lattice enthalpy?
The enthalpy change when one mole of an ionic compound is formed from its free gaseous ions.
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What is Lattice dissociation enthalpy?
The enthalpy change when one mole of an ionic compound is completely dissociated into free gaseous ions.
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What is the enthalpy of hydration?
The enthalpy change when one mole of free gaseous ions is added to an excess of water.
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What is enthalpy of solution?
The enthalpy change when one mole of an ionic compound is completely dissolved in an excess of water.
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What is entropy (ΔS)?
A measure of the disorder in a substance.
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What does the perfect ionic model of a lattice assume?
That all the ions are spherical and have their charge evenly distributed around them.
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What does it show if the experimental and theoretical lattice enthalpies for a compound are very similar?
It shows that the compound has very little covalent character.
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When will distortion most likely happen?
1.When there is high charge density on the cation(+ve), 2.When there is a large or high charge anion(-ve).
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What can cause a high charge density on the cation?
Very small cation, high charge on cation.
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What is a special case of a very small cation?
Ag+.
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What is the equation that links lattice dissociation enthalpy, Hydration enthalpy and enthalpy of solution?
Solution = Dissociation + Hydration.
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What is a spontaneous reaction?
Reactions that will occur on their own accord without the input of energy from the surroundings.
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Does a solid have high or low entropy?
Low.
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Is the entropy value of an element zero?
No.
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What could increase the entropy value?
A reaction that increases the moles or results in the formation of gas.
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What is free energy change (ΔG)?
A measure used to predict whether a reaction is feasible?
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What is the equation for free energy?
ΔG = ΔH - TΔS
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What could happen if ΔG is less than 0?
The reaction might happen by itself.
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What is the equation to work out ΔS of surroundings?
-ΔH/T
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Card 2

Front

What is the first ionisation enthalpy?

Back

The energy required to remove one electron from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+.

Card 3

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What is enthalpy of atomisation of an element?

Back

Preview of the front of card 3

Card 4

Front

What is first electron affinity?

Back

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Card 5

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What is bond dissociation enthalpy?

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