Enthalpy Flashcards Preview

Chemistry > Enthalpy > Flashcards

Flashcards in Enthalpy Deck (16)
Loading flashcards...
1
Q

enthalpy of formation

A

enthalpy change when one mole of a compound is formed from its elements under standard conditions when all products are in their standard states

2
Q

first ionisation energy definition

A

enthalpy change required to remove one mole of electrons
from one mole of gaseous atoms
to form one mole of gaseous +1 ions

3
Q

electron affinity edinition

A

enthelpy change that occurs when 1 mole of gaseous atoms
gain 1 mole of electrons
to form 1 mole of gaseous ions with a -1 charge

4
Q

enthalpy of atomisation definition

A

enthalpy change when 1 mole of gaseous atoms
is formed from the element in it’s standard state
under standard conditions

5
Q

lattice enthalpy of formation definition

A

enthalpy change when 1 mole of ionic crystal
is formed from its constituent ions
in gaseous form

6
Q

why is second ∆Hea always positive

A

energy is required to overcome repulsion between negatively charged ion and electron

7
Q

why might enthalpy values calculated from bond enthalpies be inaccurate

A

known bond enthalpies are an average of many molecules
actual bond enthalpies specific to each molecule are likely to differ from the mean values

8
Q

enthalpy of hydration definition

A

enthalpy change when 1 mole of gaseous ions become aqueous ions

9
Q

why is first ∆Hea negative

A

energy is released as the electron is attracted to the nucleus
and therefore the negative ion is more stable than the atom

10
Q

standard bond dissociation energy

A

energy required to break one mole of bonds with every substance in gaseous form

11
Q

enthalpy of solution definition

A

enthalpy change when one mole of ionic salt dissolves in a large enough volume of water so that dissolved ions do not interact

12
Q

equation linking enthalpies of solution and hydration

A

∆Hsol = ∆HLE + ∆Hhyd

13
Q

perfect ionic model assumptions (3)

A

point charges
no covalent interactions
attraction is purely electrostatic

14
Q

reasons for greater ∆HLE

A

smaller ions > charges closer
greater charges

15
Q

what does low agreement between experimental and modelled ∆HLE suggest

A

the ionic salt has some covalent character

16
Q

lattice enthalpy of dissociation definition

A

enthalpy change when one mole of ionic salt is separated into it’s constituent ions in gaseous form