Enthalpy Definitions and equations Flashcards
what is the definition of enthalpy change
Heat energy transferred in a reaction at constant pressure
what are the “standard conditions”
298K 100kpa
how many definitions do I need to remember LOLLLL
12 :0 HAHAHAHAHAHHAHAH
Enthalpy change of formation defintion
Is the enthalpy change where 1 mole of a compound is formed from its elements in their standard states under standard conditions
Bond dissociation enthalpy defintion
The enthalpy change when all the bonds of the same type in 1 molecule of gaseous molecules are broken
Enthalpy of atomisation of an element def
Enthalpy change where 1 mole of gaseous atoms is formed from an element in its standard state
Enthalpy of atomisation of a compound def
Enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms
First ionisation energy
Enthalpy change where 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms
second ionisation energy
Enthalpy change when 1 mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions
First electron affinity def
Enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms
second electron affinity
Enthalpy change when 1 mole of gaseous 2- ions is formed from 1 mole of gaseous 1- ions
Enthalpy change of hydration def
Enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions
Enthalpy change of solution def
This is the enthalpy change where 1 mole of solute is dissolved in enough solvent, that no further enthalpy change occurs on further dilution.
Lattice enthalpy of formation def
Enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions
Lattice enthalpy of dissociation def
Enthalpy change when 1 mole of a solid ionic compound, is completely dissociated into gaseous ions under standard conditions
Soluble substances tend to have (exothermic/endothermic) enthalpies of solution
Exothermic
entropy change equation
triangle s= sum of products - sum of reactants
what actually is entropy ( definition)
Entropy is the number of ways that particles can be arranged and the number of ways that energy can be shared between particles
The more particles you have the higher the….
entropy
more disorder= more entropy
Big boi positive value of entropy= WHOLE LOTTA DISORDER
Why do particles try to become disordered
To increase entropy
- As at higher entropy particles are more energetically stable
Gibbs equation ( free energy change)
delta g= delta H - T(delta s)
what happens if free energy change ( delta G) is negative or equal to zero?
Then a reaction could happen by itself
- Free energy change is used to predict whether a reaction is feasible or not.
Whats the best combination of values for the gibbs equation?
- negative delta H
- positive delta s
- As this will mean the reaction is feasible at any temperature.
What happens if delta H and delta S are both positive?
The reaction is not feasible at SOME TEMPERATURES(eg low temps)
- But may still be feasible at higher temperatures.
What happens if delta H is positive and delta S is negative
REACTION IS NOT FEASIBLE AT ANY TEMP
What happens is delta H and delta S are both negative
reaction may not be feasible at high temperatures
- But are instead feasible at low temps.
temperature and Delta H and delta S equation:
T= delta H/ delta S
- you can only use this equation when delta G is zero
Applying y= mx + c to gibbs
delta G= - delta s*t + delta H
delta g=y
negative delta s = gradient (m)
t= x value
delta H = y intercept (c)
