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Flashcards in thermodynamics Deck (32)
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1

What does Hess' law state

the enthalpy change of a reaction is independent of the route taken

2

define standard enthalpy of formation

the enthalpy change when one mole of a compound is formed from its constituent elements in standard conditions, with all products and reactants in their standard states

3

what is the standard enthalpy of an element

0

4

define standard enthalpy of combustion

the enthalpy change when one mole of a substance is completely burnt in excess oxygen

5

define standard enthalpy of atomisation

enthalpy change when one mole of gaseous atoms is formed from a compound in its standard state in standard conditions

6

define first ionisation energy

enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions

7

define second ionisation energy

enthalpy change when one mole of electrons is removed from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

8

define first electron affinity

enthalpy change when one mole of gaseous atoms gain one mole of electrons to form one mole of gaseous 1- ions

9

define second electron affinity

enthalpy change when one mole of gaseous 1- ions gains one mole of electrons to form one mole of gaseous 2- ions.

10

define lattice enthalpy of formation

enthalpy change when one mole of solid ionic lattice is formed from its constituent gaseous ions.

11

define lattice enthalpy of dissociation

enthalpy change when one mole of solid ionic lattice is dissociated into its gaseous ions

12

define enthalpy of hydration

enthalpy change when one mole of gaseous ions become hydrated/dissolved in water to infinite dilution

13

define enthalpy of solution

enthalpy change when one mole of solute dissolves completely in a solvent to infinite dilution.

14

define mean bond dissociation enthalpy

enthalpy change when one mole of covalent bonds is broken, with all species in the gaseous state

15

what is a born haber cycle

thermochemical cycle showing all the enthalpy changes involved in the formation of an ionic compound. start with elements in their standard state.

16

what factors affect the lattice enthalpy of an ionic compound

size of the ion
charge of the ion

17

how can you increase the lattice enthalpy

smaller ion
charge centres will be closer together increasing the charge. increased electrostatic forces of attraction.

18

how can born haber cycles be used to see if compounds could theoretically exists

use known data to predict certain values and then see if these compounds would be thermodynamically stable.

19

what happens when a solid is dissolved in terms of interactions of the ions with water

break lattice
gaseous ion, dissolve
surrounded by water

20

what is the perfect ionic model

perfectly spherical
even charge distribution
no covalent character

21

what kind of bonds will be the most ionic

between large positive ions and small negative ions

22

define spontaneous and feasible

it will take place of its own accord

23

is a reaction with a positive or negative enthalpy change more likely to be spontaneous

negative

24

define entropy

randomness of a system

25

units of entropy

JK-1mol-1

26

what is the second law of thermodynamics

entropy always increases, as it is overwhelmingly more likely for molecules to be disordered than ordered

27

is a reaction with positive or negative entropy change more likely to be spontaneous

positive

28

compare the general entropy for solids, liquids and gases

solids < liquids < gases

29

how do you calculate the entropy change for a reaction

sum of products entropy - sum of reactants entropy

30

gibbs free energy

delta G = delta H - Tdelta S