12 Questions
What is the definition of a catalyst, and how does it differ from the reactants at the end of the reaction?
A catalyst is a substance that alters the rate of a chemical reaction, but is chemically unchanged at the end of the reaction.
What is the main difference between heterogeneous and homogeneous catalysis?
Heterogeneous catalysis occurs when the catalyst is in a different physical phase to the reactants, whereas homogeneous catalysis occurs when the catalyst is in the same physical phase as the reactants.
What is the minimum energy required for colliding particles to result in a reaction, and what is the term for a collision that meets this energy requirement?
The minimum energy required is the activation energy (EACT), and a collision that meets this energy requirement is called an effective collision.
What is the term for the process in which a product of a reaction becomes a catalyst for the same reaction?
The term for this process is autocatalysis.
What is the instantaneous rate of a reaction, and how does it differ from the average rate of a reaction?
The instantaneous rate of a reaction is the rate at a particular point in time during the reaction, whereas the average rate of a reaction is the rate over a longer period of time.
What is the theory that involves the formation of intermediate species in homogeneous catalysis?
The theory is called the intermediate formation theory.
What is the intermediate formed between a reactant and a catalyst, and what happens to it?
An unstable intermediate is formed between a reactant and a catalyst, and it quickly breaks down to form the product, with the catalyst being regenerated in the process.
What is the difference between adsorption and absorption, and how does it relate to surface adsorption theory?
Adsorption is the accumulation of one substance at the surface of another, whereas absorption is the penetration of one substance into another. Surface adsorption theory is a type of heterogeneous catalysis where reactants adsorb onto the surface of a solid catalyst.
What is the role of active sites in surface adsorption theory, and how can they be affected by certain particles?
Active sites are areas on the catalyst surface where the reaction between reactants takes place. Certain particles, such as lead and arsenic, can block these active sites, acting as catalytic poisons.
How does the division or porosity of the catalyst affect the reaction rate, and why?
The more finely divided or porous the catalyst, the greater the reaction rate, due to the increased availability of catalytic sites.
What is the relationship between ΔH and the type of reaction, and how can it be determined?
If ΔH is negative, the reaction is exothermic, meaning heat is lost. If ΔH is positive, the reaction is endothermic, meaning heat is absorbed. This can be determined by measuring the heat change during the reaction.
What is the effect of an increase in temperature on the number of collisions and the activation energy of a reaction?
An increase in temperature of 10K would result in a small (50%) increase in the number of collisions, but no change in the activation energy.
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