Click to enlarge
When dealing with chemical reactants, three important questions are usually asked.
(1) What product(s) can be made,
(2) How much can be made and
(3) How fast can it be made.
The first question relies on knowledge about the characteristics of each reactant and being able to “predict” how they will react together. This power of prediction spans many areas of chemistry, including: inorganic, electrochemical, organic and bioorganic/biological.
In general chemistry inorganic reactions are predicted based on the formation of a solid, gas, weak or non-electrolyte using metathesis or double replacement reactions. Memorization of common gases and the solubility rules aid students in their predictions.
Electrochemical reactions, discussed in chapter 8 of the Physical Chemistry textbook, rely on the use of oxidation and reduction potentials in redox reactions. Reference tables can be used to determine which reactions will proceed and are closely linked with thermochemical constants.
Organic reactions generally deal with carbon and other non-metals and require a more in depth knowledge of oxidation and reduction, the bonding theories: valence bond theory and molecular orbital theory and the molecules environment.
Bioorganic/Biological reactions are similar but generally deal with very large molecules so the focus is on one specific reactive site.
The quantitative question, how much can be made, is first answered by understanding balanced stoichiometry and conversions between different units. Unfortunately, the question is not usually that simple.
An understanding of chemical equilibrium (covered in chapters 4 and 6 – Thermodynamics module), the balance or ratio of reactant to product, is needed before any calculation can be made. It becomes even more complex because any disturbance changes that balance.
How fast products can be made, kinetics, is a very complex question that often deals with a more detailed look at what is actually occurring inside the reaction and is the focus of both chapters 9 and 10 (Kinetics module).
Reactions are viewed as a series of steps that describe what is actually occurring that lead to the overall product. These steps do not always resemble the original equation. Each step requires a certain amount of energy, activation energy, and has a specific speed or rate.
How fast the overall reaction proceeds is ultimately determined by the slowest or rate determining step.
While basic chemical knowledge from general chemistry is required, this textbook covers each of these questions in depth.