Elementary Reactions

Mr. Andersen explains elementary reactions, focusing on molecular collisions and energy requirements. He demonstrates unimolecular, bimolecular, and termolecular reactions, discussing their rate laws and predictability. The video emphasizes the complexity of reaction mechanisms and the need to measure reaction rates.

What is required for a reaction to occur between two molecules?

• Correct orientation and sufficient energy

• Low pressure environment

• Presence of a catalyst

• High temperature only

Which of the following is an example of a unimolecular reaction?

• Photosynthesis

• A + B forming C

• Combustion of methane

• Radioactive decay of carbon-14

What is the order of a reaction where two molecules of A combine to form products?

• First order

• Zero order

• Second order

• Third order

Why are termolecular reactions considered rare?

• They require a catalyst

• They need three molecules to collide simultaneously with correct orientation and energy

• They occur only at high temperatures

• They involve complex molecules

What is the main reason reaction rates are not predictable from stoichiometry alone?

• Stoichiometry only provides the balanced equation

• Reaction rates depend on temperature

• Stoichiometry does not account for reaction mechanisms

• Reaction rates are influenced by pressure

How can the predictability of reaction rates be improved?

• By using a catalyst

• By understanding the elementary steps and molecular collisions

• By increasing the temperature

• By reducing the concentration of reactants

What is the role of intermediates in reaction mechanisms?

• They are catalysts

• They are the final products

• They are temporary species not shown in the overall reaction

• They slow down the reaction