Reaction Rates and Rate Laws

Question 1

Describe the relationship between surface area and reaction rate

Answer 1

direct; • When the surface area of a given amount of substance is increased, the reaction rate will increase
• When more material is available, the reaction will go faster

Question 2

What are the units for a reaction rate?

Answer 2

o Because the rate is defined as a change in concentration per time the units are Ms-1 (Molarity per second)

Question 3

Describe the relationship between reaction rate and temperature

Answer 3

direct; • All elementary reactions have a faster rate at higher temperatures

Question 4

What 4 factor affect reaction rate?

Answer 4

 Medium or Nature of the Reactants
 Concentration
 Temperature
 Catalyst

Question 5

What creates the energy barrier between reactants and products?

Answer 5

• The energy barrier between reactants and products means that before you can form any new bonds of the product molecules, you have to break bonds in the reactants or form some intermediate compounds that are usually higher in energy

Question 6

What does a reaction rate measure?

Answer 6

o The rate of a chemical reaction is a measure of how fast the reaction is proceeding
 Specifically, it is a measure of the change in the concentration of the chemical species as a function of time

Question 7

What is a catalyst?

Answer 7

• A catalyst is a compound that essentially changes the reaction mechanism for a reaction allowing it to proceed at a faster rate

Question 8

Why doesn’t a catalyst appear as a reactant or product?

Answer 8

• A catalyst is part of the reaction mechanism but it is not consumed during the chemical reaction and thus does not appear as a reactant or product

Question 9

What is the purpose of a catalyst?

Answer 9

• The typical role of a catalyst is to lower the energy barrier between reactants and products (activation energy) allowing the reaction to proceed at a faster rate

Question 10

What is the rate law dependent on?

Answer 10

o The rate law for a reaction is dependent on the specifics of how a reaction proceeds called the mechanism (what bond break first, what bonds form first, any intermediate chemical species)

Question 11

What is a rate law?

Answer 11

o A rate law relates the rate of a reaction to the concentration of the reactants