enthalpy changes

Question 1

enthaply change of formation

Answer 1

enthalpy change when 1 mol of a compound if formed from its elements

Question 2

Enthalpy change of atomisation of element

Answer 2

1 mol of gaseous atoms formed from its elements

Question 3

enthalpy change of atomisation of compund

Answer 3

1 mol of compound converted into gasoues atoms

Question 4

first ionisation energy

Answer 4

Energy needed to chage 1 mol of gasous atoms into 1 mol of gaseous 1+ atoms

Question 5

second ionisation energy

Answer 5

change 1 mol of gaseous 1+ atoms into +2 atoms

Question 6

first electrn affinity

Answer 6

energy needed to change one mol of gaseous atoms into 1 mol of gaseous 1- atoms

Question 7

second electron affinity

Answer 7

one mol of gaseous 1- atoms into one mol of 2- gaseous atoms

Question 8

Lattice enthaply

Answer 8

1 mol of a solid ionic compound formed from its gaseous ions

Question 9

Enthalpy change of hydration

Answer 9

1 mol of gasous ions dissolved in wotar

Question 10

enthaply change of solution

Answer 10

1 mol of solute dissolved in a solvent eg water

Question 11

Write an equation for the process that has an enthalpy change equal to the electron affinity of chlorine.

Answer 11

Cl(g) + e- → Cl-(g)

Question 12

In terms of electrostatic forces, suggest why the electron affinity of fluorine has a
negative value.

Answer 12

There is an attraction between the nucleus/protons and (the added) electron(s)
Energy is released (when the electron is gained)

Question 13

Explain why there is a difference between the hydration enthalpies of the magnesium and sodium ions.

Answer 13

magnesium (ion) has a higher charge

Question 14

Explain why the theoretical enthalpy of lattice dissociation for silver fluoride is different from the experimental value that can be calculated using a Born–Haber
cycle.

Answer 14

Experimental lattice enthalpy value allows for / includes covalent interaction / non–spherical ions / distorted ions / polarisation

Question 15

What does a larger exothermic value tell you about lattice enthalpy

Answer 15

• a stronger ionic bond

Question 16

Factors affecting lattice enthaply

Answer 16

IONIC radius and IONIC charge

Question 17

is enthaply of hydration exo or endo

Answer 17

exo

Question 18

what is entropy

Answer 18

Tells you how much disorder there is

Question 19

how to calculate entropy changes

Answer 19

product - reactants

Question 20

what is free energy change

Answer 20

measure to predict whether a reaction is feasible

Question 21

what does it mean to be feasible

Answer 21

one started reaction will carry on without any energy being supplied

Question 22

what does it mean if the free energy change is negative or 0

Answer 22

reaction is feasible

Question 23

why may a free energy change of negative or 0 not mean a reaction is feasible

Answer 23

may have really high activation energy or so slow you wouldn’t see it