17.1- ENTHALPY CHANGE Flashcards
What is the standard molar enthalpy of formation ΔfH⦵?
enthalpy change when one mole of compound formed from its constituent elements under standard conditions, all reactants + products in their standard states
What is the standard molar enthalpy change of combustion ΔcH⦵?
enthalpy change when one mole of substance completely burnt in oxygen
What is the standard enthalpy of atomisation? ΔatH⦵
enthalpy change which accompanies the formation of one mole of gaseous atoms from element in its standard state under standard conditions
What is the first ionisation energy ΔiH⦵?
standard enthalpy change when one mole of gaseous atoms converted into a mole of gaseous ions each with a single positive charge
What does the second ionisation energy refer to?
loss of a mole of electrons from a mole of singly positively charged ions
What is the first electron affinity ΔeaH⦵?
standard enthalpy change when one mole of gaseous atoms is converted to a mole of gaseous ions, each with a single negative charge
What is the second electron affinity ΔeaH⦵?
enthalpy change when a mole of electrons is added to a mole of gaseous ions each with a single negative charge to form ions each with two negative charges
What is the lattice enthalpy of formation ΔlH⦵?
standard enthalpy change when one mole of solid ionic compounds is formed from its gaseous ions
Wheat happens when a lattice forms and what is the ΔH⦵ like?
new bonds formed, resulting in energy being given out, so ΔH⦵ always negative for this process
What is the lattice enthalpy of dissociation?
standard enthalpy change when one mole of solid ionic compounds dissociated into its gaseous ions
Can lattice enthalpies be measured directly?
no
What is done as lattice enthalpies cannot be measured directly?
they’re calculated
What is the enthalpy of hydration ΔhydH⦵?
standard enthalpy change when water molecules surround one mole of gaseous ions
What is the enthalpy if solution ΔsolH⦵?
standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart not to interact with each other
What is the mean bond enthalpy?
enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds
Where are electrons transferred from to in a simple model of ionic bonding?
electrons transferred from metal atoms to non-metal atoms
What sort of ions are formed in ionic bonding?
positively charger metal ions and negatively charged non-metal ions that all have stable outer shlel of electrons
How do the positively and negatively charged ions arrange themselves in ionic bonding?
arrange themselves into a lattice so that ions of opposite charge next to one another
What happens if positively charged ions come together with negatively charged ions?
form solid lattice + energy given out due to attraction between oppositely charged ions- called lattice formation enthalpy ΔlH⦵
What does Hess’s law tell us about total energy change?
total energy change for chemical reaction same whatever route taken, provided initial and final conditions are the same
