Chapter 23 (The Transition Metals)

Question 1

Define Transition Metals

Answer 1

Elements with an incomplete d-sub shell of electrons as either an atom or an ion.

Question 2

What are the properties of transition metals?

Answer 2

Form complexes
Ions are coloured
Variable oxidation state
Can act as catalysts

Question 3

Define ligand

Answer 3

Molecule or ion that forms a coordinate bond to a metal by donating a pair of electrons

Question 4

Define Lewis acid

Answer 4

Electron pair acceptor

Question 5

Define Lewis base

Answer 5

Electron pair donor

Question 6

Define complex

Answer 6

Metal atom surrounded by ligands

Question 7

What is a coordinate number?

Answer 7

The number of coordinate bonds around a metal ion

Question 8

What are the three types of ligands?

Answer 8

Unidentate (1 coordinate bond per molecule ), bidentate (two coordinate bonds per molecule), multidentate (form multiple coordinate bonds per molecule)

Question 9

Why are coloured ions produced?

Answer 9

Some parts of the visible spectrum are absorbed and others are reflected.

Colour depends on the electron configuration of the metal ion.

Question 10

What happens to a ligand in alkaline conditions?

Answer 10

Hydrolysis of ligand so increases negative charge on the ion so continued oxidation is easier.

Question 11

What happens to a ligand in acid conditions?

Answer 11

Prevents hydrolysis from taking place and the H+ ions provide electrons to reduce the complex ion.

Question 12

What conditions are required for potassium manganate titrations?

Answer 12

Strong acid that will not act as an oxidising agent or a reducing agent.

Question 13

What is the colour change when using potassium manganate?

Answer 13

The Mn2+ ions are pale pink and colour intensifies due to excess of Mn2+ once all the Fe2+ has reacted.

Question 14

What is the colour change when using potassium dichromate?

Answer 14

Orange to green

Question 15

Write the steps for redox titrations calculations

Answer 15

1) Write the half equations for the oxidising and reducing agents
2) Use the half-equation to write a redox equation for the overall reaction
3) Use the equation to calculate the moles of the agents and their ratios.
4) Calculate the number of moles in the original solution
5) Determine the concentration of the original solution or the percentage of the reducing agent in a known quality of sample

Question 16

What is the difference between a heterogenous and homogenous catalyst?

Answer 16

Heterogenous = Different phase than reactants

Homogenous = Same phase as reactants

Question 17

How can the adsorption of a reactant onto a metal surface speed up a reaction?

Answer 17

• Weaken bonds within reactant molecule reducing the Ea
• Causes the reactant molecule to break into more reactive fragments, reducing the Ea
• Holds a reactant in a particular position increasing the chances of a successful collision
• Gives a higher concentration of reactant on the catalyst surface so the chances of a favourable collision increases

Question 18

What is meant by a poisoned catalyst?

Answer 18

Active sites are blocked

Question 19

What determines the acidity of the solution of metal ions?

Answer 19

Charge of the metal ion = larger charge = more dissociation = lower pH

Size of the metal ion = greater ionic charge:size ratio = greater dissociation = lower pH

Question 20

Define Amphoteric

Answer 20

Metal hydroxides that can react with both acid and alkalis

Question 21

What happens when ligand are replaced by ligands of a greater denticity?

Answer 21

There is an increase in entropy