5.1: Reaction Rates

Learning Objectives

• I can explain the relationship between the rate of a chemical reaction an experimental parameters.

• I can define the rate of chemical reaction as the rate at which an amount of reactants is converted to products per unit time.

• I can describe how the rate of formation of products and disappearance of reactants are determined using stoichiometric coefficients.

• I can explain how the rate of a chemical reaction is influenced by the reactant concentration, temperature, surface area and the. use of a catalyst.

What is Kinetics:

Kinetics is the study of the rate at which chemical reactions take place. Kinetics determines how fast a chemical reaction is taking place by monitoring the amount of products or reactants over time.

How do we measure the Rate of Reaction ?

The simple definition of the rate of reaction is how quickly a reaction produces products. We can measure how quickly a reaction occurs by observing concentrations.

As a reaction progresses, the concentration of the reactants decrease as they are used to create products. A reaction may start with an initial concentration of 0.5M but then after 30 seconds, that concentration may drop to 0.2M. Conversely, the concentration of the products will increase as they are created. Therefore, when dealing with a rate of reaction, it can be written mathematically as: Rate = -Δ[Reactant]/t or as Rate = Δ[Product]/t. The units for rate are mol/Ls, also notated as Ms^-1 or mol L^-1 s^-1. You may also see that seconds will change to hours, etc. You have to be sure to keep track of this!

Rate of Disappearance, Rate of Appearance and Overall Rate of Reaction