Thomson Definitions

Question 1

Lattice Enthalpy (delta H le)

Answer 1

The Enthalpy change that accompanies the formation of one mile of an ionic compound from its gaseous ions under standard conditions

Question 2

Give an equation for the lattice Enthalpy of KCl

Answer 2

K+(g) + Cl- (g) ———> KCl(s)

Question 3

Give an equation for the lattice Enthalpy of KCl

Answer 3

K+(g) + Cl- (g) ———> KCl(s)

Question 4

Standard Enthalpy of formation (delta H f)

Answer 4

The Enthalpy change that occurs when one mole of a compound is formed from its constituent elements under standard conditions. All reactants and products being in their standard states

Question 5

Give the equation of the Enthalpy of formation for KCl (s) (delta H f)

Answer 5

K(s) + 1/2Cl2 ———> KCl(s)

Question 6

Standard Enthalpy change of atomisation (delta H at)

Answer 6

The Enthalpy change that occurs when one mole of gaseous atoms form from the element on its standard state

(Making it a gas)

Question 7

Give an equation for the Enthalpy change of atomisation (delta H at)

Answer 7

K(s) ———> K(g)

Question 8

First ionisation energy (Delta H ie1)

Answer 8

The Enthalpy change accompanying the removal of one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 9

Give an equation for first ionisation energy

Answer 9

K(g) ———> K+ + e-

Question 10

Second ionisation Enthalpy (delta H ie2)

Answer 10

The Enthalpy change that accompanies the removal of one electron from each ion in one moles of gaseous 1+ ions to form one mole of 2+ gaseous ions

Question 11

Why is the second ionisation Enthalpy higher than the first

Answer 11

The outer shell of electrons is pulled in as one electron is removed. The ionic radius decreases

Question 12

Give an equation for the second ionisation Enthalpy

Answer 12

Ca+ ———> Ca2+ +e-

Question 13

Why are ionisation energies endothermic

Answer 13

Requires energy to overcome the electrostatic attraction between the negative electrons and the positive nucleus

Question 14

First electron affinity (delta H ea1)

Answer 14

The Enthalpy change accompanying the addition of one electron to each atom in one like of gaseous atoms to form one mole of 1- ions

Question 15

Equation of first electron affinity

Answer 15

Cl +e- ———> Cl-

Question 16

Second electron affinity (delta H ea2)

Answer 16

The Enthalpy change thag accompanies the addition of one electron to one mole of gaseous 1- ions to form one mole of gaseous 2- ions

Question 17

Equation for second electron affinity

Answer 17

O- + e- ———> O2-

Question 18

Why is the first electron affinity negative but the second positive

Answer 18

The first electron affinity is negative because the positive nucleus attracts the negative e-

The second is positive needs energy as the whole negative ion repels the electron