Enthalpy, entropy, free energy

Question 1

ΔLEH⦵

Answer 1

enthaply change when 1 mole of a solid ionic compound is formed from its gaseous ions

Question 2

ΔfH⦵

Answer 2

enthalpy change when 1 mole of a compound is formed from its elements

Question 3

ΔatH⦵ (element)

Answer 3

enthalpy change when 1 mole of gaseous atoms is formed from an element

Question 4

ΔatH⦵ (compound)

Answer 4

enthalpy change when 1 mole of a compound is converted to gaseous atoms

Question 5

ΔhydH⦵

Answer 5

enthalpy change when 1 moles of gaseous ions is dissolved in water

Question 6

ΔsolH⦵

Answer 6

enthalpy change when 1 mole of solute is dissolved in a solvent, such as water

Question 7

is ΔatH⦵ always endo or exothermic

Answer 7

endothermic, as bonds must be broken for it to happen

Question 8

What are standard conditions

Answer 8

100kPa (1atm) 298K (25°C)

Question 9

are first/second ionisation energies always endo or exothermic

Answer 9

endothermic, must overcome the attraction between electrons and nucleus

Question 10

is first electron affinity endo or exothermic

Answer 10

exothermic

Question 11

is second electron affinity endo or exothermic

Answer 11

endothermic

Question 12

what are the 2 factors that affect lattice enthalpy

Answer 12

-ionic charge -ionic radius

Question 13

how does ionic charge effect lattice enthalpy

Answer 13

higher charges on ions -> stronger electrostatic attraction between ion -> more energy released when lattice forms -> more negative enthalpies

Question 14

how does ionic radius effect lattice enthalpy

Answer 14

smaller ionic radii of ions formed, higher the charge density of the ion. greater electrostatic attraction between ions, so lattice more exothermic.

Question 15

how do you calculate ΔsolH⦵

Answer 15

-ΔLEH + ΣΔhydH

Question 16

draw an enthalpy cycle for calculating the enthalpy change of solution

Answer 16

Question 17

how do you calculate entropy change (ΔS)

Answer 17

ΔS = Sproducts - Sreactants

Question 18

how do you calculate free energy change (ΔG)

Answer 18

ΔG = ΔH - TΔS

Question 19

how do you calculate the temp at which a reaction becomes feasible

Answer 19

ΔT = ΔH/ΔS

Question 20

is a reaction with a negative ΔH but positive ΔS feasible/ maybe feasible or never

Answer 20

always feasible

Question 21

is a reaction with a positive ΔH and positive ΔS feasible/ maybe feasible or never

Answer 21

maybe, only above certain temp

Question 22

is a reaction with a negative ΔH but negative ΔS feasible/ maybe feasible or never

Answer 22

maybe, only below certain temp

Question 23

is a reaction with a positive ΔH but negative ΔS feasible/ maybe feasible or never

Answer 23

never feasible

Question 24

draw an enthalpy cycle for calculating the enthalpy change of solution

Answer 24

Question 25

define average bond enthalpy

Answer 25

energy need to break 1 mole of a bond in the gas phase, average over the different compounds that the bond is found in.