C17 - Thermodynamics

Question 1

What is the standard enthalpy of formation?

Answer 1

Standard enthalpy of formation is theenthalpy changewhen1 mole of a compoundis formed from itselementsunder standard conditions (298 K temperature and 100 kPa pressure). The reactioncan beendothermicorexothermic

Question 2

What is the standard enthalpy of combustion?

Answer 2

Standard enthalpy of combustion is theenthalpy changewhen1 mole of a substanceundergoes complete combustion (is burnt in excess oxygen) under standard conditions, with all substances being in their standard states. The reactionis always exothermic

Question 3

What is the standard first ionisation enthalpy?

Answer 3

Thestandard first ionisationenthalpyis the enthalpy change for the conversion of 1 mole of gaseous atoms to 1 mole of gaseous cations, each atom losing an electron under standard conditions. Ionisation enthalpyis endothermic as energy is need to overcome the attraction between an electron and the nucleus

Question 4

What is the standard first enthalpy of electron affinity?

Answer 4

Thestandardfirst enthalpy of electron affinity is theenthalpy changefor the conversion of one mole of gaseous atoms into one mole of gaseous anions, each atom gaining one electron under standard conditions. Reaction is exothermic as there will be attraction between the electron and the nucleus

Question 5

What is the standard second electron affinityenthalpy change?

Answer 5

Thesecond electron affinity is theenthalpy changefor the conversion of one mole of gaseous 1- ions into one mole of gaseous 2- ions, each atom gaining one electron under standard conditions. The second electron affinity is always endothermic, as energy is needed to add an electron to an already negative ion

Question 6

What is thestandardenthalpy change of atomisation?

Answer 6

Thestandardenthalpy change of atomisation is theenthalpy changewhen1 moleof gaseous atomsis formed from itselementunder standard conditions. The reactionis alwaysendothermicas energy is always required tobreakany bonds between the atoms in the element

Question 7

What is the standard bond dissociation enthalpy?

Answer 7

The bond dissociation enthalpy is the enthalpy change when 1 mole of a covalent bond is broken under standard conditions in the gaseous state. The reactionis alwaysendothermicas energy is requiredto break bonds

Question 8

What is the standard lattice formation enthalpy?

Answer 8

Standard lattice formation enthalpy is the enthalpy change for the formation ofone moleof solidioniccompound from its constituent gaseous ions at standard conditions. The reaction is alwaysexothermic,as when the ions arecombinedthere is an extremely large release of energy