Transition Metals as Catalysts

what is A homogeneous catalyst

the same state as the reactants

what is A heterogeneous catalyst

different state to the reactants.

why is transitional metal good catalyst

variable oxidization states

how does homogenous catalyst work

The catalyst reacts, forms an intermediate, and is then regenerated. 

This alternative reaction route requires lower activation energy than if the reactants had to react directly.

how does heterogenous catalyst work

The reactants adsorb to, react on, and desorb from the active sites.

why best to trurn catalyst into powder or coating with a support medium

increases its surface area, and the number of active sites.

decrease costs

why important to purify reactants

because impurities bind to a catalyst’s active sites and poison it.

3 catalyst need to know

The Contact Process (heterogeneous catalysis)

Iodide and peroxydisulfate (homogeneous catalysis)

Manganate and ethanedioate (autocatalysis)

The contact process

SO₂(g)+V₂O₅(s)→SO₃(g)+V₂O₄(s)

V₂O₄(s)+ 1/2 O₂(g)→V₂O₅(s)

What is the catalyst in the contract process

Vanadium (V) oxide acts as a heterogeneous catalyst, providing both active sites and an alternative reaction route.

How sulfur trioxide turned into sulfuric acid

SO3(g)+H2SO4(l)→H2S2O7(l)

H2S2O7(l)+H2O (l)→2H2SO4(l)

why does Iodide and peroxydisulfate reaction do not proceed without a catylst

This reaction does not proceed uncatalysed because both reactants are negatively-charged.

Iodide and peroxydisulfate

S₂O₈^2-(aq)+2Fe²⁺(aq)→2 SO₄^2-(aq)+2Fe³⁺(aq)

2Fe³⁺(aq)+2I^-(aq)→2Fe²⁺(aq)+I₂(aq)

catalyst in Iodide and peroxydisulfate

We use iron (II) ions as a homogeneous catalyst

iron’s variable oxidation states allow this alternative reaction route.

why we use catalyst in Manganate and ethanedioate

In acidic conditions, this reaction does proceed without a catalyst, but only slowly.

Manganate and ethanedioate

8Mn²⁺(aq)+2MnO₄^-(aq)+16H⁺(aq)→10Mn³⁺(aq)+8H₂O (l)

10Mn³⁺(aq)+5C₂O₄^2-(aq)→10Mn2+(aq)+10CO₂(g)

catalyst in Manganate and ethanedioate

In the first step

, Mn²⁺ and MnO₄^-​ attract each other and react to form Mn³⁺

In the second step, Mn³⁺ oxidises ethanedioate and Mn²⁺is regenerated.