Lecture 2

Question 1

What is a latimer diagram?

Answer 1

• a latimer diagram is a summary of the standard electrode potential data of an element
• The most highly oxidised form of the element is on the left, with successively lower oxidation states to the right
• The species are connected by arrows and each arrow is labelled with the numerical value of the standard potential for that reduction

Question 2

What is comproportionation?

Answer 2

where two reactants containing the same element but with different oxidation numbers, form a compound having an intermediate oxidation number
This is favourable is the middle oxidation state in set of 3 is in a ‘valley’ on the frost diagram

Question 3

What is disproportionation?

Answer 3

when an element is both oxidised and reduced in the same reaction

Question 4

what is a frost diagram?

Answer 4

A frost diagram summarises the energetics of the half reaction in which a species X with oxidation number N is converted to its elemental form for all the different oxidation numbers that are accessible to the element

Question 5

What do you find on the axis’ of a frost diagram?

Answer 5

Y-axis= NE value for converting from a given oxidation state to the elemental form
X-axis= oxidation state value
The plot has an origin 0,0 because the elemental form with N=0 has NE=0

Question 6

What does the gradient of the line in a frost diagram represent?

Answer 6

the gradient of the line between any 2 points on a frost diagram gives the potential for the reaction

e.g. Ecell= 0.521-0/1-0= 0.521V

Question 7

What happens if a point lies outside of the line in a frost diagram?

Answer 7

A specie that lies in a peak, above the gradient of the 2 points on side side, denotes a species unstable with respect to disproportation

Question 8

How do you calculate nE and NE values?

Answer 8

see pg17 of handout