M3 Chapter 9 - Enthalpy Flashcards
(26 cards)
Define enthalpy change of formation.
Enthalpy change when 1 mole of a compound is formed from its elements in standard states under standard conditions.
Define enthalpy change of combustion.
The enthalpy change when 1 mole of a substance combusts, with all reactants and products in their standard states under standard conditions.
Define enthalpy change of neutralisation.
Enthalpy change when 1 mole of water is formed from the reaction of a acid and base under standard conditions.
Define enthalpy change of atomisation of an element.
Enthalpy change when 1 mole of gaseous atoms are formed from an element in its standard state.
Define enthalpy change of atomisation for a compound.
Enthalpy change when 1 mole of gaseous atoms are formed from a compound in its standard states.
Define first ionisation enthalpy.
Enthalpy change when 1 mole gaseous atoms forms 1 mole of gaseous 1+ ions.
Define second ionisation enthalpy.
Enthalpy change when 1 mole of gaseous 1+ ions forms 1 mole of gaseous 2+ ions.
Define first electron affinity.
Enthalpy change when 1 mole of gaseous ions forms 1 mole of gaseous 1- ions.
Define second electron affinity.
Enthalpy change when 1 mole of gaseous 1- ions forms 1 mole of gaseous 2- ions.
Define enthalpy change of hydration.
Enthalpy change when 1 mole of aqueous atoms are formed from 1 mole of gaseous atoms.
Define enthalpy change of solution.
Enthalpy change when 1 mole of a solute is dissolved in sufficient solvent so no further enthalpy change takes place.
Define lattice enthalpy.
Enthalpy change when 1 mole of an ionic compound is formed from its gaseous ions in standard conditions.
What does lattice enthalpy measure?
Ionic bond strength.
State standard conditions.
1 atm
298K (25C + 273)
1 moldm-3
Define average bond enthalpy.
Enthalpy change when 1 mole of bonds are broken in gaseous molecules.
What does a system in a reaction mean?
The atoms and bonds involved in a chemical reaction.
Explain the law of conservation.
The amount of energy in an isolated system remains the same. Energy cannot be created nor destroyed, it can only be transferred from one form to another.
Breaking bonds and making bonds = what energy changes?
BendoMexo
What is an endothermic reaction?
A reaction with overall positive AH. Ie: enthalpy of products is greater than enthalpy of reactants.
What is an exothermic reaction?
A reaction with an overall negative AH. Ie: enthalpy of products is less than enthalpy of reactants.
What does activation energy mean?
The minimum energy required for a reaction to take place.
What does standard state mean?
The state at which an element is in, under standard conditions.
Give an example of a reaction that shows enthalpy change of formation.
H2 + 1/2O2 –> H2O
How to work out enthalpy change from experimental data?
q=mcΔT
m = mass of substance being heated
c = 4.18
ΔT = change in temperature
