A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy. It is not consumed in the reaction.

Define homogeneous catalyst .

A homogeneous catalyst is one that is in the same phase as the reactants. For example, a catalyst dissolved in the same liquid solution as the reactants.

True or False? A catalyst is consumed during a chemical reaction.

False. A catalyst is not consumed. It provides an alternative reaction pathway but is regenerated at the end of the reaction and does not appear in the overall chemical equation.

Define heterogeneous catalyst .

A heterogeneous catalyst is one that is in a different phase to the reactants. A common example is a solid catalyst used with gaseous or liquid reactants.

A catalyst increases the rate of reaction by lowering the .......... energy, so a greater .......... of molecules have sufficient energy for an effective collision.

A catalyst increases the rate of reaction by lowering the activation energy, so a greater proportion of molecules have sufficient energy for an effective collision.

How does a catalyst affect the Boltzmann distribution curve and the rate of reaction?

The Boltzmann distribution curve shape is unchanged (the temperature is the same). However, the lower E a means the area under the curve to the right of E a is larger, so a greater proportion of molecules can react and the rate increases.

Give one example each of a homogeneous catalyst and a heterogeneous catalyst used in industrial chemistry.

Homogeneous: concentrated H 2 SO 4 (acid) in esterification reactions (same liquid phase as reactants). Heterogeneous: iron catalyst in the Haber process (solid catalyst with gaseous N 2 and H 2 reactants).

True or False? A catalyst changes the enthalpy change (ΔH) of a reaction.

False. A catalyst only lowers the activation energy and provides an alternative pathway. The overall enthalpy change (Δ H ) between reactants and products is unchanged .

On a reaction profile, the catalyst lowers the .......... of the transition state peak but does not change the energy of the .......... or the .......... .

On a reaction profile, the catalyst lowers the height of the transition state peak but does not change the energy of the reactants or the products .

A LevelChemistryCambridge (CIE)Flashcards8. Reaction KineticsHomogeneous & Heterogeneous Catalysts

Homogeneous & Heterogeneous Catalysts (Cambridge (CIE) A Level Chemistry): Flashcards

Exam code: 9701

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Cards in this collection (9)

Define catalyst.
A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy. It is not consumed in the reaction.
Define homogeneous catalyst.
A homogeneous catalyst is one that is in the same phase as the reactants. For example, a catalyst dissolved in the same liquid solution as the reactants.
True or False?
A catalyst is consumed during a chemical reaction.
False.
A catalyst is not consumed. It provides an alternative reaction pathway but is regenerated at the end of the reaction and does not appear in the overall chemical equation.
Define heterogeneous catalyst.
A heterogeneous catalyst is one that is in a different phase to the reactants. A common example is a solid catalyst used with gaseous or liquid reactants.
A catalyst increases the rate of reaction by lowering the .......... energy, so a greater .......... of molecules have sufficient energy for an effective collision.
A catalyst increases the rate of reaction by lowering the activation energy, so a greater proportion of molecules have sufficient energy for an effective collision.
How does a catalyst affect the Boltzmann distribution curve and the rate of reaction?
The Boltzmann distribution curve shape is unchanged (the temperature is the same). However, the lower E_a means the area under the curve to the right of E_a is larger, so a greater proportion of molecules can react and the rate increases.
Give one example each of a homogeneous catalyst and a heterogeneous catalyst used in industrial chemistry.
Homogeneous: concentrated H₂SO₄ (acid) in esterification reactions (same liquid phase as reactants).
Heterogeneous: iron catalyst in the Haber process (solid catalyst with gaseous N₂ and H₂ reactants).
True or False?
A catalyst changes the enthalpy change (ΔH) of a reaction.
False.
A catalyst only lowers the activation energy and provides an alternative pathway. The overall enthalpy change (ΔH) between reactants and products is unchanged.
On a reaction profile, the catalyst lowers the .......... of the transition state peak but does not change the energy of the .......... or the .......... .
On a reaction profile, the catalyst lowers the height of the transition state peak but does not change the energy of the reactants or the products.

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