Reactivity 1.2 Energy Cycles in Reactions
No description yet. This curated deck is ready for daily study.
Card preview (17)
What state are bond enthalpies in?
Gaseous
What does bond breaking involve
Separating atoms that are attracted by an electrostatic force, requires energy
What does bond forming involve
Bringing together atoms that are attracted by an electrostatic force, releases energy.
Average bond enthalpy strength order
single covalent bond< double cb< triple cb
Hess’s Law of constant heat summation
The total energy change in a chemical reaction depends only on the initial and final states and is independent of reaction pathway.
Standard enthalpy of atomisation of an element
The enthalpy change when one mole of gaseous atoms are formed from the element in its gaseous state
Enthalpy of formation
The enthalpy change when one of product is formed from its constituent/separate elements in their standard state.
First ionisation energy
The minimum energy required to remove one mole of electrons from one mole of gaseous atoms (or ions for 2nd IE) to form one mole of gaseous ions.
Electron affinity
The energy released when one mole of gaseous atoms acquire an electron to form one mole gaseous ion.
Lattice Enthalpy
The energy needed to convert one mole of ionic solid into gaseous ions under standard conditions.
Enthalpy of Atomisation
The enthalpy change that occurs when one mole of gaseous atoms is formed from the elements in its standard state. (turning an element in its ss into a gas)
Calculating enthalpy of atomisation and dissociation for diatomic molecules
Halve the bond enthalpy values in the data booklet.
Infinite dilution
A solution that is already so diluted that adding more water isn’t going to change the conc.
Enthalpy of solution
The enthalpy change when one mole of a solute is dissolved in solvent to infinite dilution at STP. (solid–>aq ions).
Steps of enthalpy of solution
Lattice enthalpy (lattice–>ions (g)) then enthalpy of hydration (hydrates ions (g) to make them aq).
Enthalpy of hydration
The enthalpy change when one mole of gaseous ions is dissolved to form an infinitely dilute solution of one mole of aq ions. (gaseous ions–>aq ions)
Enthalpy of dissociation
The amount of energy required to break a chemical bond between two species.