Chem 1b Flashcards
Dynamic equlibrium
The concentrations of all substances are constant and the rate of the forward reaction equals the rate of the reverse reaction.
Le Chateliers Principle
If a change is made to a reaction at eqm. then the position of equilibrium will change so as to oppose that change if possible.
Enthalpy change
The amount of heat energy taken in or given out during any change in a system at constant pressure.
Standard enthalpy change
The enthalpy change for a reaction at 298 K and 100 kPa with all reactants and products in their standard states.
Specific heat capacity
The heat required to raise the temperature of 1 gram of a substance by 1 Kelvin. It is measured in J g–1 K–1.
Standard enthalpy of combustion
Enthalpy change which occurs when 1 mole of a substance is completely burnt in oxygen at 298K and 100kPa.
Standard enthalpy of formation
Enthalpy change which occurs when 1 mole of a substance is formed from its elements at 298K and 100kPa.
Bond dissociation enthalpy
Enthalpy change when 1 mole of a specific bond in a specific gaseous molecule is broken at 298 K and 100 kPa.
Mean bond enthalpy
The average amount of energy needed to break a covalent bond averaged over a range of gaseous compounds at 298 K and 100 kPa.
Enthalpy change of solution
Enthalpy change when 1 mole of an ionic substance dissolves in water to give a solution of infinite dilution.
Infinitely dilute solution
There is a sufficiently large excess of water that adding any more doesn’t cause any further heat to be absorbed or evolved
Hydration enthalpy
Enthalpy change when 1 mole of gaseous ions dissolve in sufficient water to give an infinitely dilute solution. Hydration enthalpies are always negative.
Lattice enthalpy
Enthalpy change during the formation of one mole of an ionic compound from its oppositely charged gaseous ions under standard conditions.
Why does lattice enthalpy decrease as ions get bigger?
Charge remains consistent, but size:charge ratio decreases so there are weaker attractions between the cation and the anion.
Enthalpy change using formation data
Products - reactants
