lattice enthalpy

Question 1

lattice enthalpy def

Answer 1

the enthalpy change that accompanies the formation of 1 mole of ionic lattice from its gaseous ions.

Question 2

lattice enthalpy is exo or endo?

Answer 2

exothermic (-) as energy is given out when ionic bonds are being formed from gaseous ions

Question 3

the more negative the value of lattice enthalpy…

Answer 3

the stronger the electrostatic forces of attraction between the oppositely charged ions in the lattice

Question 4

does a covalent substance have lattice enthalpy?

Answer 4

no because there are no ions in the structure

Question 5

define standard enthalpy change of formation

Answer 5

the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states

Question 6

standard enthalpy change of formation is exo or endo?

Answer 6

exothermic (-) as energy is released in bond making

Question 7

define standard enthalpy change of atomisation

Answer 7

the enthalpy change when one mole of gaseous atoms is formed from its elements in its standard state

Question 8

standard enthalpy change of atomisation is exo or endo?

Answer 8

endothermic (+) as bonds have to be broken

Question 9

define first ionisation energy

Answer 9

the enthalpy change when one mole of gaseous 1+ ions is formed from gaseous atoms

Question 10

first and second ionisation energy is exo or endo?

Answer 10

endothermic (+) as the electron being lost has to overcome attraction from the nucleus in order to leave the atom

Question 11

define second ionisation energy

Answer 11

one mole of gaseous 2+ ions are formed from one mole of gaseous 1+ ions

Question 12

define first electron affinity

Answer 12

one mole of gaseous 1- ions is formed from gaseous atoms

Question 13

first electron affinity is exo or endo?

Answer 13

exothermic (-) because the electron is attracted into the outer shell of an atom by the nucleus

Question 14

define second electron affinity

Answer 14

one mole of gaseous 2- ions is formed from gaseous 1- ions

Question 15

second electron affinity is exo or endo?

Answer 15

endothermic (+) because the negative electron being added is repelled by the negative 1- ion so energy is needed to overcome the repulsion

Question 16

define standard enthalpy change of solution

Answer 16

the enthalpy change when one mole of compound is dissolved in water to form an infinitely dilute solution

Question 17

standard enthalpy change of solution is exo or endo?

Answer 17

can be both - if LE is greater than HYD then it it endothermic (+), if LE is less than HYD then it is exothermic (-)

Question 18

define standard enthalpy change of hydration

Answer 18

the enthalpy change when one mole of gaseous ions is dissolved in water to form an infinitely dilute solution

Question 19

standard enthalpy of hydration is exo or endo?

Answer 19

exothermic (-) as ionic bonds are broken and bonds are made between the cation/anion and a water molecule

Question 20

what are the two energy changes in the dissolving process?

Answer 20

1. the ionic lattice breaks up (opposite enthalpy change to LE therefore endothermic)
2. water molecules are attracted to and the surround the ions (the separate gaseous ions interact with polar H2O to form hydrated aq ions therefore exothermic)

Question 21

entropy def

Answer 21

the measure of dispersal of energy in a system

Question 22

feasibility def

Answer 22

whether a reaction is able to happen and is energetically feasible (spontaneous)

Question 23

(ΔG) free energy def

Answer 23

overall change in energy in energy during a chemical reaction AND MADE UP OF ΔH (enthalpy change) and TΔS (entropy change a the temperature of the reaction )