C24 - Inorganic reactions Flashcards
What colour are Vanadium 5+ ions?
Yellow
What colour are Vanadium 3+ ions?
Green
What colour are Vanadium 4+ ions?
Blue
What colour are Vanadium 2+ ions?
Violet
What is the equation for the redox titration between Fe2+and MnO4- and what is the colour change?
5Fe2++ MnO4−+ 8H+⟶ Mn2++ 5Fe3++ 4H2O
Colourless to pale pink
What is a catalyst?
A catalyst is a substance that speeds up reactions by providing an alternative reaction route with lower activation energy
Why do transition metals make good catalysts?
They show variable oxidation states. This allows them to act as intermediates in the exchange of electrons between reacting species
They also provide a surface for reactions to occur. The metal forms weak bonds to the reacting species, holding them in place
What are homogeneous catalysts?
Homogeneous catalysts are in the same phase as the reaction species
What are heterogeneous catalysts?
Heterogeneous catalysts are in a different phase to the reaction species
What is the catalyst in the Haber process and is it homogeneous or heterogeneous?
Iron
Heterogenous
What is the heterogeneous catalyst in the contact process (making sulfur trioxide)?
The catalyst is vanadium (V) oxide (V2O5)
2SO₂ + O₂ → 2SO₃
Reactions with catalysts:
SO₂ + V₂O₅ → SO₃ + V₂O₄
2V₂O₄ + O₂ → 2V₂O₅
What is the catalyst in producing methanol?
Catalyst is chromium (III) oxide
CH4 + H2O → CO +3H2
CO(g) + 2H2(g) → CH3OH(g)
What is the catalyst in the reaction between Iodine and peroxodisulfate?
Catalyst is Iron (II)
(S₂O₈)²⁻ + 2I⁻ → I₂ + 2(SO₄)²⁻
Reactions with catalyst:
S₂O₈²⁻ + 2Fe²⁺ → 2SO₄²⁻ + 2Fe³⁺
2Fe³⁺ + 2I⁻ → 2Fe²⁺ + I₂
What is autocatalysis?
Autocatalysis is when one of the products of a reaction acts as a catalyst for the reaction
What happens to the rate of reaction in autocatalysis?
Initially the rate of an auto catalysed reaction is very slow, but as the product increases, the reaction rate increases
How do heterogeneous catalysts work?
They adsorb one or more of the reactants onto their surface. The partially filled d-sub levels form very weak bonds with the reactants, so the reaction can occur. The products are then desorbed from the catalyst surface
What happens to a heterogeneous catalyst over time?
A catalyst can be poisoned as it becomes blocked by impurities, as strong bonds with a substance are formed, so the catalyst strops working
