A2 Catalysts

In which one of the following reactions is a heterogeneous catalyst not used?

• N₂ + 3H₂ → 2NH₃

• CO + NO → CO₂ + N₂

• CO₂ + C → 2CO

• SO₂ + O₂ → SO₃

what is the catalyst in the Contact Process?

• Vanadium metal

• vanadium (V) oxide

• iron

• vanadium (II) oxide

The reaction between aqueous persulphate ions, , and iodide ions, I^–(aq), is catalysed by Fe²⁺(aq) ions. Suggest why this reaction has a high activation energy.

• the catalyst increases the activation energy

• iodide ions are good reducing agents

• the bond enthalpy of persulfate ions is very high

• both ions are negatively charged and repel

What is a homogeneous catalyst?

• a catalyst in the same phase as the reactants

• a catalyst in a different phase to the reactants

• a singularly fantastic catalyst

• iron

Why might a support medium be used with a heterogeneous catalyst?

• to allow the reaction to occur at the surface of the catalyst

• to help it stand up

• to reduce the amount of catalyst needed and reduce cost

• to increase the amount of catalyst needed and reduce the cost

what is meant by the term autocatalysis?

• a reaction that starts itself

• a reaction with a very low activation energy

• a reaction in which a reactant acts as a catalyst

• A reaction in which a product acts as a catalyst

Identify the species which acts as an autocatalyst in the reaction between ethanedioate ions and manganate(VII) ions in acidic solution.

• Mn²⁺

• MnO₄^-

• ethanedioate

• H⁺

Identify a transition metal used in catalytic converters and state how the converter is constructed to maximise the effect of the catalyst.

• Ni

• Rh

• Fe

• V

State the characteristic property of transition metals that enables them to act as catalysts in redox reactions.

• can form complexes

• ability to form coloured compounds

• variable oxidation state

• have high melting points

Suggest why ions from s block elements do not usually act as catalysts.

• their compounds are white

• too reactive

• their melting points are too low

• only exist in one oxidation state