Therodynamics Flashcards
What is atomisation enthaply and what type of reaction is it
The energy needed to produce one mole of free gaseous atoms of that atom in standard conditions and in its standard states and it’s endothermic
1/2Cl2(g)->Cl(g)
Na(s)->Na(g)
What is first ionisation energy and what type of reaction is it
The amount of energy needed to remove one electron from each mole of free gaseous atoms of that element to form positive ions it’s exothermic
Na(g)->NA+(g)+e-
What is first electron affinity and what type of reaction is it
The energy change when one electron is added to each of a mole of free gaseous atoms of that element for negative ions it’s exothermic
Cl(g)+e->Cl-(g)
What is second ionisation energy of an element
The energy needed to remove one electron from each mole of free positive ions of that element
Mg+(g)->Mg2+(g)e-
What is second electron affinity of an atom and what type of reaction is it
Its the energy change when one mole of electrons are added to a mole of gaseous atoms each with a single negative charge to form ions each with 2nd negative charges
It’s exothermic
O-(g)+e->O2-(g)
What is lattice enthalpy of formation
It’s a standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions
Na+(g)+Cl-(g)->Nacl(s)
What is enthaply of lattice dissociation and state the type of reaction it is
Is standard enthalpy change when one mole of solid ionic compound is dissociated into its gaseous ions
It’s endothermic (+)
What is enthaply of hydration
Its the standard enthalpy change when water molecules surround one mole of gaseous ions and become aqa ions
Na+(g) +aq->Na+(aq)
What is enthaply of solution
Standard enthalpy change when one mol of an ionic compound dissolves completely in water to form a solution in which don’t interact with one another
NACL-NACl(aq)
What reaction does this represent
Mg (s)->Mg (g)
Standard enthalpy of atomisation
What reaction does this represent
Mg(g)->Mg+ (g)+e-
First ionisation energy
What is mean bond enthaply
Energy change when I mole of gaseous molecules each break a covalent bond which is averaged over a range of compounds
Why are atomisation enthalpies endothermic
As bonds in the element need to be broken
Why are second ionisation energies more endothermic than first ionisation energies
As there is less repulsion between the remaining electrons in the ion so more energy is needed to remove the electrons
Why are second electron affinities endothermic
As the incoming electron is repelled by the negative charge on the ion so the value is positive
Why are lattice enthalpies of formation negative and why are lattice enthalpies of dissociation positive
Ionic bonds are being formed so it’s exothermic
Ionic bonds are being broken so it’s endothermic
State the two ways to work amount enthaply change of solution
Hydration - lattice of formation
Hydration +lattice of dissociation
What is entropy and how do you work it out
It’s the degree of disorder of a system higher degree the more stable it is
Products - reactant
State what will become of the reaction when entropy is positive or negative
If entropy is positive the reaction is more likely
If it’s negative it’s less likely to occur
State the free energy equation and what each symbol stands for
G=H-TS
G is change in free energy
H is change in enthaply
A change in entropy
If G is positive what will happen
The reaction will not proceed
If G is negative what will happen
The reaction will occur
What will happen to the reaction of enthaply is negative and entropy is positive
The reaction is spontaneous at all temperature because theirs more disorder due to increasing entropy
If enthaply is positive and entropy is negative what will happpen
The reaction won’t be spontaneous at any temperature
What does it mean for the reaction if both entropy and enthalpy are positive
It means the reaction will be spontaneous above a certain temperature
What does it mean if both enthaply and entropy are both negative
The reaction will only be spontaneous below a certain temperature
How would you work out temperature in Gibbs free energy
T=H/S
Which types of lattices have the higher lattice enthalpies
Smaller lattices this is because the cations and anions are closer together so they attract together more closely
How is entropy worked out
Products - reactants
In Gibbs free energy how is entropy worked out
Enthaply/Temperature
What is the perfect ionic model
It’s spherical shaped with only electrostatic forces of attractions with ionic bonds
What causes differences with the theoretical and experimental lattice enthalpies and what is the cause of this
When a compound shows covalent character which is caused by polarisation
State the type of reaction hydration enthalpies are and what factor cause some elements to have higher hydration enthalpies than others and why
They are exothermic reactions
They higher the charge density the greater the hydration enthalpy this id because ions attract water molecules more strongly
What causes polarisation
The negative ion because distorted and more covalent because of that metal cation causes polarisation
What tendencies cause covalent character
Small positive ion-because
Positive ion having multiple charges
Negative ion being large meaning outer shell electrons to be less attracted
Negative ions has multiple negative charges
State why when a solid dissolves it will be more spontaneous
As entropy increases because theirs more disorder
Increases entropy means more particles
This makes G more negative
What does this represent
CL2->2Cl
Bond disassociation so we divide by 2
Why is enthaply hydration exothermic
As bonds are made between ions and water which releases energy
When will substances have zero entropy
When temperature is absolute 0
