Heterogenous Catalysts

Question 1

Transition Metals use as Catalysts

Answer 1

Make good catalysts because they can change oxidation states by gaining or losing electrons within their d orbitals.

This means they can transfer electrons to speed up reactions

Question 2

Explain the contact process

Two Equations for the Contact Process

Answer 2

Vanadium (V) oxide oxidises SO2 to SO3 because it can be reduced to vanadium (IV) oxide.
Then oxidised back to V (V) oxide by oxygen ready to start all over again.

V2O5 + SO2 –> V2O4 + SO3

V2O4 + 1/2 O2 –> V2O5

Question 3

Heterogenous Catalyst

Answer 3

A catalyst that is in a different phase from the reactants (ie in a different physical state)

Question 4

Example of a heterogenous catalyst reaction

Describe the surface area of the reaction and active sites

Answer 4

eg in Haber Process gases are passed over a solid iron catalyst.

The reaction happens on active sites located on the surface of the heterogenous catalyst.

So increasing the surface area of the catalyst increases the number of molecules that can react at the same time, increasing the rate of reaction

Question 5

Support Mediums

Answer 5

Often used to make the area of the catalyst as large as possible.

They help to minimise the cost of the reaction, because only a small coating of a catalyst is needed to provide a large surface area

Question 6

Equation for Haber Process

Used to make

Answer 6

N2 + 3H2 –> 2NH3

Ammonia

Question 7

Equation for Contact Process catalyst

Used to make

Answer 7

SO2 + 1/2 O2 –> SO3.

(the SO3 reacts with water) to make Sulfuric Acid

Question 8

Impurities and Heterogenous Catalysts

Explain

Name of process

Answer 8

Heterogenous catalysts often work by adsorbing reactants onto active sites located on their surfaces.

Impurities in the reaction mixture may also bind to the catalyst’s surface and block reactants from being adsorbed.

Catalyst poisoning

Question 9

Catalyst Poisoning

Effect

Answer 9

Reduces the surface area of the catalyst available to the reactants, slowing down the reaction.

Catalyst poisoning increases the cost of a chemical process because less product can be made in a certain time or with a certain amount of energy.

The catalyst may even need replacing or regenerating costing money

Question 10

Sulfur and catalyst poisoning of the Haber Process

Answer 10

The hydrogen in the haber process is produced from methane.

The methane is obtained from natural gas, which contains impurities, including sulfur compounds.

Any sulfur that is not removed is adsorbed onto the iron, forming iron sulphide, and stopping the iron from catalysing the reaction efficiently