thermodynamics

Question 1

what is enthalpy of atomisation?

Answer 1

= enthalpy change when 1 mole of gaseous atom is formed from its elements under standard states
= this is the same for solid into gas, sublimation

Question 1

what is the enthalpy change of formation?

Answer 1

= enthalpy change when 1 mole of substance is formed from its elements undert standard conditions and standard states

Question 2

What is bond dissociation enthalpy?

Answer 2

= standard molar enthaloy change when one mole of covalent bond is broken into two gaseous atoms or ree radicalsm

Question 3

what is the first ionsation energy?

Answer 3

= amioung of energy required to remove 1 mole of electron from 1 mole of a gaseous atom

Question 4

What is second ionisation energy?

Answer 4

= amount of energy required to remove 1 mole of electron from 1 mole of a gaseous +1 ion

Question 5

What is first electron affinity?

Answer 5

= enthaly change when 1 mole of gaseous atom gains 1 mole of electron to form 1 mole of gaseous atom with -1 charge
= exothermic, attraction between nucleus (specify) and extra electron

Question 6

What is second electron affinity?

Answer 6

= enthalpy change when 1 mole of gaseous -1 atom gains one electron per ion to produce 2- ion
= endothermic, takes energy to overcome repulsive force between negative ion and electron

Question 7

What is enthalpy of lattice formation?

Answer 7

= standard enthalpy change when 1 mole of an ionic crystal lattice is formed from it’s constituent ions in gaseous form

Question 8

What is enthalpy of lattice dissociation?

Answer 8

= standard enthalpy change when 1 mole of an ionic crystal lattice form is seperated into its constituent ions in gaseous form

Question 9

What is enthalpy of hydration?

Answer 9

= enthalpy change when one mole of gaseous ions becomes aqeous ions
= this always gives out energy, exothermic because bonds are made between ions and water molecules

Question 10

What is enthalpy of solution?

Answer 10

= standatd enthalpy change when 1 mole of ionic solid dissolves in large enough water to ensure that all the dissolved ions are well seperated and do not interact with one another

Question 11

What is the perfect ionic mode in relation to the assumtpions made for theotretical lattice enthalpies?

Answer 11

= ions are 100% ionic
= spherical
= attractions are purley electrostatic
= theoritrcl lattice enthlapies and born haber will be the same.

Question 12

What are the differences between theoretical and born haber experimental lattice enthalpies?

Answer 12

= the born haber alttic enthaloy is the real experimental value,
= when a compound shows covalent chatacter the thoetrical and born haber lattice enthaloies differ
= the more the covalent chaacter the bigger the difference in values

Question 13

What does the strength of the enthalpy of lattice formation depends on?

Answer 13

= size of ions: larger the ions the less negative the enthalpies of formation- as ions get bigger the charges becomes firther apart so weaker forces of attraction
= charges on the ioN; the bigger the charge on the ion, the greater attraction between the ions, so the stronger the lattice enthalpy

Question 14

What does it look like if it is 100% ionic?

Answer 14

= ions are spherical
= theoretical and born haber lattice, enthalpies will be the same

Question 15

What does ionic with covalent character look like?

Answer 15

= charge cloud is distorted
= theoretical, and experimental born haber will difer

Question 16

What is a spontaneous reaction?

Answer 16

= proceed on its own without external influence

Question 17

What is problem with enthalpy?

Answer 17

= reaction that is exothermic, result in products that are more thermodynamically stable, than the reactants
= driving force between many reactions, and causes them to be spontaneous,

Question 18

What is entropy?

Answer 18

= number of ways atoms, can share quanta energy
= substances with more ways of arranging their atoms and energy have higher entropy

Question 19

What leads to a positive entropy change?

Answer 19

= increase in disorder and entropy will lead to a posiive entropy change

Question 20

What causes a significant increwase in entropy?

Answer 20

= thereis a change in state from liquid to gas
= signigicant increase in number of molecules from reactants to prodycts

Question 21

How do we caluclate the delta s?

Answer 21

= entropy of the products- reactanys

Question 22

Do elements in their standard states have an entropy of 0?

Answer 22

= no. only perfect crystals

Question 23

What determines feasability?

Answer 23

= gibbs energy=
enthalpy change - temperature (entropy)
= we use kelvins
= S will always be Joules, conervy to k by dividing by 1000
=

Question 24

Whenis the reaction feasible?

Answer 24

= if the gibbs free energy is negative
= this will ne negative for any spontaneous change

Question 25

What us gibbs energy if there is a phase change like melting and boiling?

Answer 25

= it is 0

Question 26

What happens if there is a decrease in entropy?

Answer 26

= negative
= increasing temperature will make it less likley gibbs energy is negatieve, so not feasible, abd kess likley for the reaction to occur
=WHat

Question 27

What happens if the entropy is close to 0?

Answer 27

= temperature will not have a large effect, on feability
= as -T^s will be small, and gibbs will not change much

Question 28

What happens if there is an increase in entropy?

Answer 28

= increasing temperature will make it more likeyly, gibbs will be negative and and more likely the reaction occurs.

Question 29

How can the gibbs energy equation rewlate to y=mx+C?

Answer 29

= enthalpy change is the y intercept
= the gradient of the graph is -entropy
=
= a positive gradient means entropy is negative,
= if gibbs is below 0, this mans the reaction is spontaneous
=