Transition metals

Question 1

Why are Transition metals good catalysts?

Answer 1

They can change oxidation states

Question 2

What is autocatalysis?

Answer 2

The product of the reaction acts as a catalyst for the same reaction. As the reaction progresses, the amount of product increases and the reaction SPEEDS UP.

Question 3

Give an example of a homogenous autocatalysis reaction

Answer 3

Reaction between C2O42- and MnO4- ions
The reactant ions are both negative, so repel each other, causing a very slow rate of reaction
2MnO4-(aq) + 16H+(aq) + 5C2O42-(aq) → 2Mn2+(aq) + 8H2O(l) + 10CO2(g)
The Mn2+ ions produced catalyse the reaction
MnO4-(aq) + 4Mn2+(aq) + 8H+(aq) → 5Mn3+(aq) + 4H2O(l)
2Mn3+(aq) + C2O42-(aq) → 2Mn2+(aq) + 2CO2(g)

Question 4

What is a heterogenous catalyst?

Answer 4

Heterogeneous catalyst – different physical state to the reactants (usually reactants in gas or solution and the catalyst is solid)

Question 5

What are catalytic converters

Answer 5

• Reduce emissions of carbon monoxide and nitrogen monoxide
• They use a platinum or rhodium catalyst to convert these gases into nitrogen and carbon dioxide
• Has a honeycomb structure to create a larger surface area
  2NO(g) + 2CO(g) → N2(g) + 2CO2(g)

Question 6

Problem with CO and NO

Answer 6

> CO
- Formed from incomplete combustion in engines
- Poisonous gas
- Binds irreversibly to the haemoglobin so oxygen cannot be transported
NO
- Formed from the reaction between atmospheric O2 and N2 due to the very high temperatures in an engine
- Oxidises to NO2 – respiratory irritant/acid rain

Question 7

Why is water a mondentate ligand and not bidentate?

Answer 7

Water’s chain is too short

Question 8

Why, in terms of entropy, is a reaction feasible?

Answer 8

More particles on the right of the equation therefore
ΔS∘sys is positive/increases

Question 9

Why do transition metals show a variety of oxidation numbers?

Answer 9

There is only a gradual increase in successive ionisation energies