Redox Reactions

Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid-base reactions. Fundamentally, redox reactions are a family of reactions that are concerned with the transfer of electrons between species. Like acid-base reactions, redox reactions are a matched set -- you don't have an oxidation reaction without a reduction reaction happening at the same time. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons. Each reaction by itself is called a "half-reaction", simply because we need two half-reactions to form a whole reactions. Here a video to explain more!

Clues that a Chemical Reaction has Occuured

It may be hard to recognize that a chemical reaction has occurred but there are some indicators that tell you for sure. Some reactions produce a distinct smell or odor that may indicate when a reaction is occurring. an example my be if you go outdoors after a thunderstorm, you may detect an unusual odor in the air. The odor is an indication that lightning has caused a chemical change in the air.A change in temperature may also indicate a chemical reaction such as the temperature is higher near logs burning in a campfire. A change in color is often an indication of a chemical change. For example, fruit may change color when it ripens. Formation of bubbles as shows a reaction has taken place. The formation of gas bubbles is another indicator that a chemical change may have occurred.
Formation of a solid or precipitate shows a chemical reaction has taken place When two liquids are combined, a solid called a precipitate can form. The shells of animals such as clams and mussels are precipitates. They are the result of a chemical change involving substances in seawater combining
with substances from the creatures.

Double Replacement Reactions

A double displacement reaction, also known as a double replacement reaction or metathesis, is a type of chemical reaction where two compounds react, and the positive ions (cation) and the negative ions (anion) of the two reactants switch places, forming two new compounds or products. Learning these is quite simply if you understand and follow your solubility rules and exceptions.

Chemical Reactions

I was a bit nervous about starting this unit because I figured it would be the hardest so far, but it really isn't all that bad. Most of it is math based rather than rule based so its easy to pick up on. I'm hoping for a good exam grade.  All I need to do to ensure a good grade is to remember the poly-atomic ions that have made a reoccurring appearance in the new lessons.

Solubility Rules

A basic knowledge of which compounds are soluble in aqueous solutions is essential for predicting whether a given reaction might involve formation of a precipitate (aka a solid). The solubility rules are essential in remembering if a compound can be dissolved in water or not. Here are the rules:


Rule 1. All compounds of Group IA elements (the alkali metals) are soluble.

Rule 2. All ammonium salts (salts of NH4+) are soluble.

Rule 3. All nitrate (NO3-), chlorate (ClO3-), perchlorate (ClO4-), and acetate (CH3COO- or C2H3O2-, sometimes abbreviated as Oac-) salts are soluble.

Rule 4. All chloride (Cl-), bromide (Br-), and iodide (I-) salts are soluble except for those of Ag+, Pb2+, and Hg22+.

Rule 5. All sulfate ( SO4=) compounds are soluble except those of Ba2+, Sr2+, Ca2+, Pb2+, Hg22+, and Hg2+, Ca2+ and Ag+ sulfates are only moderately soluble.

Rule 6. All hydroxide (OH-) compounds are insoluble except those of Group I-A (alkali metals) and Ba2+, Ca2+, and Sr2+.

Rule 7. All sulfide (S2-) compounds are insoluble except those of Groups I-A and II-A (alkali metals and alkali earths).

Rule 8. All sulfites (SO3=), carbonates (CO3=), chromates (CrO4=), and phosphates (PO43-) are insoluble except for those of NH4+ and Group I-A (alkali metals)(see rules 1 and 2).