energy

Question 1

enthalpy change of formation

Answer 1

standard enthalpy change of formation is the energy transferred when 1 mole of a compound is formed from its elements under standard conditions and all reactants and products in their standard states
negative

Question 2

enthalpy change of atomisation

Answer 2

enthalpy change when 1 mole of gaseous atoms formed from its elements under standard states

Question 3

first ionisation enthalpy

Answer 3

enthalpy change required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a 1+ charge

Question 4

second ionisation enthalpy

Answer 4

enthalpy change to remove 1 mole of electrons from one mole of gaseous 1+ ions to produces one mole of gaseous 2+ ions.

Question 5

first electron affinity

Answer 5

enthalpy change when 1 mole of gaseous atoms gain 1 mole of electrons to form 1 mole of gaseous ions with a 1- charge
exo for atoms that normally form negative ions as ion more stable than atom and there’s an attraction between nucleus and atom

Question 6

second electron affinity

Answer 6

enthalpy change when one mole of gaseous 1- ions gain one electron per ion to produce gaseous 2- ions
endothermic for oxygen as it takes energy to overcome repulsive force between negative ion and electron

Question 7

lattice enthalpy

Answer 7

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

Question 8

enthalpy of hydration

Answer 8

when one mole of gaseous ions become aqueous ions
always eco because bonds made between ions and water molecules

Question 9

enthalpy of solution

Answer 9

enthalpy change when one mole of ions solid dissolves in large enough amount of water to ensure all dissolved ions are well separated and do nt interact with eachother

Question 10

lattice dissociation

Answer 10

ec when 1 mol ionic compound separates into its gaseous ions

Question 11

The first ionisation energy of sodium is more endothermic than that of potassium. Explain why.

Answer 11

sodium has a smaller atomic radius so greater nuclear attraction

Question 12

The lattice enthalpy of sodium oxide is more exothermic than that of potassium oxide. Explain why.

Answer 12

ionic radius of sodium is smaller
so attracts to 02- more strongly

Question 13

Predict how the enthalpy changes of hydration of F− and Cl− would differ.

Answer 13

Enthalpy of hydrogenation of fluorine more negative than cl
f- has a smaller size so greater attraction to co2

Question 14

Predict and explain the effect, if any, of the larger volume of water on the following: * The temperature change, ΔT
The calculated value of ΔsolH for H2SO4.

Answer 14

temperature decreases as same energy spread over larger volume

delta solution the same as same energy released per mol h2so4

Question 15

How would the lattice enthalpies of magnesium chloride and calcium chloride differ?

Answer 15

lattice enthalpy of mgcl2 more exo than cacl2

as magnesium ion is smaller and has a greater charge density than ca

so attraction between magnesium ions and chlorine ions greater than between calcium ions and chlorine ions

Question 16

average bond enthalpy

Answer 16

when one mole of bonds

of (gaseous covalent) bonds is broken

Question 17

what does strength of lattice formation depend on

Answer 17

the size of the ions - larger less negative enthalpies of lattice formation
as ions are larger charges further apart weaker attractive force between them
the charges on the ion
bigger charge means greater attraction between ions so stronger lattice enthalpy

Question 18

∆S ̊ formula

Answer 18

∆S ̊ = Σ S ̊products - ΣS ̊reactants

Question 19

Gibbs and temp - increase temp

Answer 19

increase temp more likely Gibbs negative and more likely reaction occurs

Question 20

y= mx+c to the ∆G = ∆H - T∆S equation.

Answer 20

c = ∆H and the gradient is equal to -∆S

Question 21

is lattice dissociation endo or exo and why

Answer 21

ionic substances dissolve in lattice they must be broken up
endo thermic as energy needed to break lattice

Question 22

are hydration enthalpies exo or endo and why

Answer 22

exothermic
energy given out as water molecules bond to metal ions
negative ions attracted to positive h

Question 23

what happens when a salt ΔH solution is exothermic

Answer 23

salt dissolves at any temp
G is always negative
H is negative