Chemistry Unit 5 Module 2

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Energy transferred when one mole of a compound is formed from its elements under standard conditions
Enthalpy change of formation
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Enthalpy change when one mole of gaseous ions is formed from the element in it's standard state
Enthalpy change of atomisation
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Enthalpy change required to remove electrons from one mole of gaseous atoms to form one mole of 1+ ions
First ionization energy
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Enthalpy change required to remove electrons from one mole of gaseous 1+ atoms to form one mole of 2+ ions
Second ionization energy
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Enthalpy change when electrons are added to one mole of gaseous atoms to form one mole of 1- ions
First electron affinity
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Enthalpy change when electrons are added to one mole of gaseous 1- ions to form one mole of gaseous 2- ions
Second electron affinity
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Standard enthalpy change when one mole of an ionic compound is formed from its constituent elements in gaseous ions
Lattice enthalpy
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Enthalpy change when one mole of gaseous ions become aqueous ions
Enthalpy change of hydration
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Enthalpy change when one mole of an ionic solid dissolves
Enthalpy change of solution
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Why is the second electron affinity negative?
It takes energy to overcome the repulsive force between the negative ion and the electron
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Ca2+ (g) +e-+O- (g) -> Ca2+ (g) + O2- (g)
Second electron affinity
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What two factors effect lattice enthalpy
Size and charge of the ions
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What effect does a smaller sized ion have on lattice enthalpy and why?
Smaller the ion the greater, more negative, the value of lattice enthalpy. Smaller the ion the greater the attractive force between them due to a greater charge density.
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What effect does have a weaker charge have on lattice enthalpy and why?
Weaker the charge, the smaller, less negative, the value of lattice enthalpy. This is because there is less attraction between the ions and a weaker charge density.
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What is Entropy?
A measure of disorder, the greater the entropy the more disordered the system is.
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Rank Solids, gases and liquids in order of most disorder to more ordered.
Gases, liquids then solids
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A positive value of entropy shows?
An increase in disorder
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A negative value of entropy shows?
An increase in order
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An increase in moles on the products results in an increase or decrease of entropy?
Increase
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Equation for entropy
∆S ̊ = Σ S ̊products - ΣS ̊reactants
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Unit for entropy
J K-1 mol-1
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When will 0 entropy occur?
Only perfect crystals at 0K (absolute zero) will have zero entropy
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Gibbs free energy equation
∆G = ∆H - T∆S
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∆G must be what in order for the reaction to be spontaneous
negative
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when ∆H is negative and ∆S positive, ∆G will...
always be negative
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when ∆H is negative and ∆S negative, ∆G will...
only be negative at low temps
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when ∆H is positive and ∆S positive, ∆G will...
only be negative at high temps
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when ∆H is positive and ∆S negative, ∆G will...
never be negative
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How do you calculate the temperature at which a reaction would be feasible?
Make ∆G = 0 and then solve for T
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The loss of electrons
Oxidation
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The gain of electrons
Reduction
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Redox is when...
a reaction has both reduction and oxidation occur
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Br2 (aq) + 2I- (aq) -> I (aq) + 2 Br- (aq), what's the reducing agent?
Iodide ion
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2 (aq) + 2I- (aq) -> I (aq) + 2 Br- (aq), what's the oxidising agent?
Bromine
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Reducing agents are?
Electron donors, being oxidised
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Oxidising agents are?
Electron acceptors, being reduced
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What makes up an electrochemical cell?
Two half cells, connected by a salt bridge. The metal electrodes submerged in a solution of their ions.
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Define the term standard electrode potential
The emf of a half cell when compared to a standard hydrogen half cell under standard conditions
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What are the standard conditions of a half cell?
298K, 100kPa and 1M solution (1moldm-3)
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The more negative electrode will?
Oxidise with it's half equation going from right to left
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The more positive electrode will?
Reduce with it's half equation going from left to right
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A half cell is feasible when...
The more negative electrode is being oxidised and the more positive being reduced.
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The strongest oxidising agents are...?
The most positive as they're being reduced
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The strongest reducing agents are...?
The most negative as they're being oxidised
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Ecell = ?
E(more negative / less positive) – E (more positive / less negative)
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There are three types of cell, what are they?
Rechargeable, non-rechargeable and fuel cells
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Energy from the reaction of a fuel with oxygen to create a half cell
A fuel cell
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Advantages of fuel cells
Less CO2 and greater efficiency
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Limitations of hydrogen fuel cells
Storing, limited lifetime, high production costs and use of toxic chemicals in their production
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Ways hydrogen can be stored in fuel cells
A liquid under pressure, adsorbed on the surface of a solid material or absorbed within a solid material
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Overall reaction of a hydrogen fuel cell?
2H2 + O2 -> 2H2O E= 1.23V
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Other cards in this set

Card 2

Front

Enthalpy change when one mole of gaseous ions is formed from the element in it's standard state

Back

Enthalpy change of atomisation

Card 3

Front

Enthalpy change required to remove electrons from one mole of gaseous atoms to form one mole of 1+ ions

Back

Preview of the front of card 3

Card 4

Front

Enthalpy change required to remove electrons from one mole of gaseous 1+ atoms to form one mole of 2+ ions

Back

Preview of the front of card 4

Card 5

Front

Enthalpy change when electrons are added to one mole of gaseous atoms to form one mole of 1- ions

Back

Preview of the front of card 5
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