Catalysts Flashcards
What is a catalyst?
A substance that increases the rate of reaction by providing an alternative reaction pathway which has a lower activation energy without being used up after the reaction
Heterogenous catalyst
A catalyst that is in a different phase which reaction occurs at the surface of the catalyst
Examples of heterogenous catalysts
Fe catalyst in haber process
Ni in hydrogenation of Alkene to alkane
What does the contact process manufacture?
Sulfur trioxide gas which is used to make Sulphuric acid
Catalyst used in the Contact process?
V₂O₅
What gases are used in the contact process?
2 moles of sulfur dioxide to 1 mole of oxygen
First step of the contact process
Sulfur dioxide and oxygen are passed over the surface of the V2O5 catalyst
Sulfur dioxide + V2O5 ——> sulfur trioxide + V2O4
Second step of the contact process
Reformation of the V2O5 catalyst
V2O4 +1/2O2 makes V2O5
Change in V oxidation state during the contact process
+5 in V2O5 to +4 in V2O4
Then reforms to +5 in V2O5
How does V2O5 act as a catalyst?
Provides an alternative reaction pathway with a lower activation energy
By reducing V5+ to V4+
What do catalytic converters do?
Convert carbon monoxide and nitrogen monoxide from internal combustion engines to less harmful gases N2 and CO2
Stages of catalytic converter reaction on surface
Adsorption of NO and CO to surface of catalyst
Weakening of bonds in a chemical reaction and formation of new bonds
Desorption of CO2 and N2 from surface of catalyst by temporary bonds breaking
Homogenous catalyst
Is in the same phase as the reactant molecules
Example of homogenous catalyst
Fe2+ or Fe3+ in solution to the reaction between
I- and S₂O₈²⁻ ——> 2SO₄²⁻ + I2
Fe2+ catalysis of I- and S₂O₈²⁻
2Fe2+ S₂O₈²⁻ ——> 2SO₄²⁻ + 2Fe3+
2Fe2+ +2I- ——> I2 +2Fe2+
So Fe2+ is reformed
Fe3+ catalysis of I- and S₂O₈²⁻
2Fe3+ + 2I- ——> I2 + 2Fe2+
2Fe2+ + S₂O₈²⁻ ——> 2SO₄²⁻ + 2Fe3+
