ENTHALPY AND ENTROPY

Question 1

Lattice enthalpy of formation definition

Answer 1

enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions

Question 2

Enthalpy change of 1st ionisation

Answer 2

enthalpy when 1 mole of gaseous 1+ ions are made from 1 mole of gaseous atoms

Question 3

How does the size of ions affect strength of ionic bond

Answer 3

the smaller the ionic radii, the stronger the electrostatic attraction between ions as they can pack together much closer so melting and boiling points are much higher

THE HIGHER THE CHARGE DENSITY THE STRONGER THE ELECTROSTATIC ATTRACTION

Question 4

Enthalpy change of solution definition

Answer 4

When 1 mole of an ionic substance is dissolved in the minimum amount of solvent to ensure no further enthalpy change is observed upon further dilution

Question 5

Enthalpy change of hydration

Answer 5

the enthalpy change when 1 mole of aqueous ions is made from 1 mole of gaseous ions

Question 6

How to work out enthalpy change of solution

Answer 6

Lattice dissociation enthalpy + enthalpy change of hydration

Question 7

2 things that affect the enthalpy change of hydration

Answer 7

the larger the charge the more exothermic, the smaller the ion the more exothermic

Question 8

What is entropy

Answer 8

the measure of disorder of a system

the number of ways energy can be shared out between particles

Question 9

How does the number of particles affect entropy

Answer 9

more particles means a higher entropy as there are more ways that energy can be distributed

Question 10

How can a reaction be feasible

Answer 10

if the changes in entropy overcome the changes in enthalpy

as increasing entropy is energetically favourable

Question 11

How would an equation show that a reaction is entropically favourable

Answer 11

a higher amount of moles on one side means that direction is favourable as there are more particles, so more ways energy can be distributed

also creating liquids or gases from solids is entropically favourable

a positive entropy entropy value is favourable

Question 12

Entropy change formula

AND UNITS

Answer 12

Entropy change = entropy of products - entropy of reactants

Joules per Kelvin per mole

Question 13

Standard conditions of enthalpy

Answer 13

1 mole of substance
298 K
100 kPa

Question 14

Gibbs free energy formula and what does it show

and what are units

Answer 14

Shows whether a reaction is feasible or not

^G = ^H - T^S

^G = enthalpy change(J/mol) - Temperature(K) x Entropy change(J/K/mole)

units are J/mol

if ^G is negative or 0 then a reaction is feasible