Textbook Unit 1.6

Question 1

what is enthalpy change

Answer 1

heat energy transferred in a reaction at constant pressure

Question 2

what are standard conditions (2) and what is its symbol

Answer 2

298K and 300kPa
a small empty circle with a line thru

Question 3

what reaction has a negative delta H

Answer 3

exothermic cus heat is given out

Question 4

Enthalpy change is the name given to the amount of heat evolved or absorbed in a reaction carried out at constant pressure. It is given the symbol ΔH, read as “delta H”

Question 5

what reaction has a positive delta H

Answer 5

endothermic because heat is absorbed

Question 6

what is enthalpy change of formation

Answer 6

Delta f H is the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard condition

Question 7

what is enthalpy change of atomisation of an element

Answer 7

delta at H is the enthalpy change when 1 mole of gaseous atoms are formed from an element in its standard state

Question 8

what is first ionisation energy

Answer 8

Delta ie1 H is the enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms

Question 9

what is first electron affinity

Answer 9

Delta ea1 H is the enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms

Question 10

what is enthalpy change of hydration

Answer 10

Delta hyd H is the enthalpy change when 1 moles of aqueous ions is formed from 1 mole of gaseous ions

Question 11

what is bond disassociation enthalpy

Answer 11

Delta diss H is the enthalpy change when all the bonds of the same type in 1 mole of gaseous molecules are broken

Question 12

what is enthalpy change of atomisation of a compound

Answer 12

Delta at H is the enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms

Question 13

what is second ionisation energy

Answer 13

Delta ie2 H is the enthalpy change when 1 mole of gaseous 2+ ions are formed from 1 mole of gaseous 1+ ions

Question 14

what is second electron affinity

Answer 14

Delta ea2 H is the enthalpy change when 1 mole of gaseous 2- ions is formed from 1 mole of gaseous 1- ions

Question 15

what is the enthalpy change of solution

Answer 15

Delta solution H is the enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution

Question 16

what is lattice enthalpy

Answer 16

a measure of ionic bond strength

Question 17

how many ways can lattice enthalpy be defined

Answer 17

Delta lattice H can be defined in 2 ways

Question 18

what is the first definition of lattice enthalpy

Answer 18

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

Question 19

what is the second definition of lattice enthalpy of dissaciation

Answer 19

the enthalpy change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions under standard conditions

Question 20

what does Hess’s law say about total enthalpy change

Answer 20

Says the total enthalpy change of a reaction is always the same regardless of the route taken

Question 21

cant calculate an enthalpy so what do you use

Answer 21

Born haber cycle

Question 22

what is the born haber cycle

Answer 22

1) start with the enthalpy of formation

2) then put the enthalpies of atomisation and ionisation energy above this

3) the electron affinity goes up here

4) lattice enthalpy done

Question 23

how many routes can you take to get from the elements in their standard states to the ionic lattice

Answer 23

2

Question 24

what does the green arrow usually show in Born haber cycle

Answer 24

direct route

Question 25

what does the purple arrow usually show in the born haber cycle

Answer 25

indirect route