Thermodynamics

Question 1

Lattice formation enthalpy

Answer 1

Enthalpy change when 1 mol of a solid ionic compound is formed from its gaseous ions

Question 2

standard enthalpy of formation

Answer 2

the enthalpy change when one mole of a substance is formed from its elements under standard conditions with substances in standard states

Question 3

second electron affinity and why is it always endothermic

Answer 3

enthalpy chance when 1 mole of elements is added to 1 mole of gaseous 1- ions to from 1 mole of gaseous 2- ions

always endothermic because energy is needed to overcome repulsion between e- and negative ion

Question 4

Hess’ law

Answer 4

enthalpy change of a reaction is independent of the route taken

Question 5

first ionisation energy

Answer 5

enthalpy change when 1 mole of electrons is removed from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 6

bond dissociation enthalpy

Answer 6

enthalpy change to break the bond in 1 mole of gaseous molecules to form gaseous atoms

bond found in only one molecules don’t have to be averaged

Question 7

second ionisation energy

Answer 7

enthalpy change when 1 mole of electrons is removed from 1 mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Question 8

mean bond enthalpy

Answer 8

enthalpy change when 1 mole of a given covalent bond is broken, averaged over a range of compounds

Question 9

first electron affinity and why is it exothermic

Answer 9

enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of gaseous 1- ions

first one if exothermic due to the attraction between electron and nucleus

Question 10

the standard enthalpy of combustion

Answer 10

enthalpy change when one mole of a substance is completely combusted in excess oxygen under standard conditions and standard states

Question 11

enthalpy change

Answer 11

heat energy change at constant pressure

Question 12

standard enthalpy of atomisation

Answer 12

enthalpy change for the formation f 1 mole of gaseous atoms from the element in its standard state

Question 13

perfect ionic model

Answer 13

ions are perfect spheres
purely ionic bonding
no covalent character-> with covalent character bond is stronger

Question 14

Gibbs free energy

Answer 14

Delta G=Delta H-TdeltaS
Delta H= enthalpy change
delta S= entropy change
T= temperature in K

negative or 0 reaction is feasible

Question 15

entropy

Answer 15

measure of disorder
increase in disorder in a reaction it is considered to be feasible

gas is state of highest disorder solid is lowest disorder

increase in mols is an increase in disorder

more disorder the more positive entropy

Question 16

enthalpy of hydration and trend

Answer 16

enthalpy change when one mole of gaseous ions become aqueous ions

more exothermic the stronger the attraction between ion and part of water molecule with opposite partial charge
factors
-charges on ion
-sizes of ion

Question 17

enthalpy of solution

Answer 17

enthalpy change when one mole of a solid dissolves in water to form aqueous ions

Question 18

enthalpy of lattice dissociation

Answer 18

enthalpy change to separate 1 mol of a solid ionic compound into gaseous ions

Question 19

About lattice enthalpies and factors

Answer 19

measure of the strength of attraction between ions

the more exothermic the stronger the attractions
more energy given out in formation lattice and more energy needed to dissociate it.
factors
-charges on ions
-size of the ions