ch 5 energetics

Question 1

define enthalpy change of combustion

Answer 1

the enthalpy change when 1 mole of substance is combusted in excess oxygen.
(under standard state)

Question 2

define enthalpy change of formation

Answer 2

the enthalpy change when 1 mole of products are formed from its constituent elements in their standard state.
(under standard state)

Question 3

define average bond enthalpy

Answer 3

the energy required to break 1 mole of gaseous covalent bonds, that are averaged over similar compounds having the same bond.

Question 4

define lattice enthalpy

Answer 4

the energy required to break 1 mole of an ionic lattice into its constituent gaseous ions.

Question 5

define hydration enthalpy

Answer 5

the enthalpy change when 1 mole of gaseous ions is solvated by solvent molecules

(e.g X- (g) + (aq) –> X- (aq))

Question 6

define ∆ enthalpy of solution

Answer 6

the enthalpy change when 1 mole of substance is dissolved in water to give a solution

Question 7

define electron affinity

Answer 7

the energy released when 1 mole of electrons is gained by 1 mole of gaseous atoms.

(in standard state)

Question 8

describe relationship between ∆H(hyd), ∆H(sol) and lattice enthalpy

Answer 8

∆H(sol) = ∆H(lat) + ∆H(hyd)

Question 9

define entropy

Answer 9

distribution of the total energy among particles of a system

Question 10

define Gibbs free energy, and its unit in the equation
∆G = ∆H - T∆S

Answer 10

energy available to do work

unit in equation = kJ