Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
29 Cards in this Set
- Front
- Back
What is enthalpy change? |
Heat change in a reaction under constant pressure |
|
What is lattice formation enthalpy? |
Enthalpy change when 1 mole of a solid ionc lattice formed from its gaseous ions under standard conditions |
|
What is the issue with lattice enthalpy? |
Can't be measured directly |
|
What is enthalpy change of formation? |
Enthalpy change when 1 mole of a compound is formed from its consitituent elements under standard conditions reactants and products in standard states |
|
What is bond dissociation enthalpy? |
Enthalpy change when all the bonds of the same type in one mole of gaseous molecules are broken to produce free radicals |
|
What is the enthalpy of atomisation of an element? |
The enthalpy change when 1 mole of gaseous atoms are formed from an element in its standard state |
|
What is the enthalpy of atomisation of a compound? |
Enthalpy change when 1 mnole of a compound in standard state separated into gaseous atoms |
|
What is the 1st ionisation enthalpy? |
Enthalpy change when 1 mole of electrons removed from 1 mole of gaseous atoms to form one mole of gaseous 1+ ions |
|
What is electron affinity? |
Enthalpy change when 1 mole of gaseous 1- ions formed from 1 mole of gaseous atoms |
|
What is the enthalpy change of hydration? |
Enthalpy change when 1 mole of aqueous ions formed from 1 mole of gaseous ions under standard conditions |
|
What is the enthalpy of solution?
|
Enthalpy change when 1 mole of solute(ionic solid) is dissolved in sufficient solvent such that no further enthalpy change occurs on further dilution - ions are separated and do not interact |
|
What is Hess' Law? |
Enthalpy change for a raction is the same independent of route by which reaction occurs |
|
How can Born Haber cycles be used to predict if a compound exists? |
If enthalpy of formation is very endothermic unlikely to form as less stable |
|
Explain why the second electron affinity has a large positive value. |
electron added to a negative ion so energy is required to overcome electrostatic repulsion |
|
Explain why sodium forms a stable oxide of na+ and O2- ions byt not NaO or Na(1)O |
Na(2)O requires second ionisation of sodium, endothermic change enthalpy of formation less negative NaO less electrostatic attraction so enthalpy of formation less negative |
|
Why is a compound insoluble? |
Hydration enthalpy is less than lattice dissociation enthalpy enthalpy of solution is positive |
|
Why is the enthalpy of hydration negative? |
Attraction between polar water molecules and ions = formation of bonds |
|
How can you measure bond dissociation enthalpy? |
spectroscopy |
|
Why do mean bond enthlapy calculations give diff enthalpy values than experimental? |
Experimental more accurate/specific to compound mean taken as a average over range of compound bond enthalpy diff in each compopund due to diff environment |
|
What is a spontaneous change? |
A reaction that will occur in one direction with no additional input of energy |
|
What are the units of entropy? |
J/K/mol |
|
What things affect the entropy of a molecule? |
Physical state How complicated |
|
What is entropy? |
A measure of disorder of particles - number of ways they can be arranged and energy can be shared |
|
Why can we define absolute standard entropies? |
All particles have 0 entropy at 0K No disorder/no movement |
|
What are the units for free energy change? |
J/mol |
|
What is free energy change? |
Predicts if a reaction is feasible. is feasible if less than or equal to 0 |
|
Why does dissolving increase entropy? |
particles can move freely |
|
Why do gases have a higher entropy? |
More disorder Particles move more rapidly and randomly and can be more randomly earranged |
|
what can you say about the bonding character of rubidium chloride if lattice enthalpy change of formation is similar to that calculated using a Born Haber cycle? |
Little covalent character ions are sperical/point charges and no polarisation |