Synthesis reactions occur when two substances ,generally elements, combine to form a compound.

To solve a synthesis reaction:
Two single elements are separated on the reactant side, when this equation is solved on the product side the two elements combine and become one.
1.) choose elements (set up equation)
2.) write them separately on the reactant side
3.) solve the equation for a final answer on the product side( elements should be combined together)
4.) use the crossover rule to determine if the oxidation charges need to be exchanged or cancelled

A decomposition reaction occurs when a compound breaks up into elements or in a few to simpler compounds.

To solve a decomposition reaction:
The equation will consist of a compound on the reactant side, when the equation is solved the product side will contain the compound decomposed into two separate elements.
1.) choose the elements (set up equation)
2.) on the reactant side the elements should be set up as a compound
3.) use the crossover rule to exchange or cancel out the oxidation charges
4.) solve the equation for the answer on the product side (elements should be broke down or decomposed on the product side)

In a single replacement reaction one element replaces another in a compound. A metal can replace a metal (+) or a nonmetal can replace a nonmetal. (-)

To solve a single replacement reaction:
On the reactant side there will be one single element and a compound. When the equation is solved on the product side the single element will replace one of the elements of the compound.
1.) set up the equation (this equation should contain three elements)
2.) on the reactant side there should be a single element and a compound of two non metals or two metals
3.) for the compound on the product side use the crossover rule to exchange oxidation charges
4.) on the reactant side exchange the single element from the product with the first element of the compound

In a double replacement a metal replaces a metal in a compound and a non metal replaces a nonmetal in a compound.

To solve:
There are four elements that make up this equation. They are separated into two compounds. Once solved the compounds will exchange elements that can be metals or no metals.
1.) set up the equation ( use appropriate elements)
2.) the compounds will exchange the second element of the compound to solve the equation
3.) use the cross over rule (if needed) to exchange oxidation charges
4.) on the product side the equation will stay contain two compounds but with the opposite elements

A combustion reaction is made up of hydrocarbon and oxygen. Once it is reacted it produces carbon dioxide and water.

To solve a combustion reaction:
In this equation the reactant side contains a fuel source (CxHy) and this is known as hydrocarbons. The reactant side also contains an element of oxygen. When the equation reacts it will yield carbon dioxide and and water.
1.) set up the equation ( use appropriate elements)
2.) in a combustion reaction you will never use the crossover rule
3.) to produce the product side you only need to yield carbon dioxide and water as the products

Chemical reactions occur when bonds ( between the electrons of atoms) are formed or broken. Because of the principle of, CONSERVATION of MATTER, the equation must have the same number of atoms and same kind on both sides. This principle states that matter cannot be created or destroyed. Energy changes are written in endothermic and exothermic reactions- law of CONSERVATION of ENERGY. Chemical equations are balanced when ions or atoms on the reactant side equal the same on the product side.

1.) write the correct formula for the reactants and products
2.) find the number of atoms for each element on the left side
3.) determine where to place coefficients in front of formulas so that the left side equals the same number of atoms on the right side.
****the numbers in front of the elements are called STOICHIOMETRIC COEFFICIENTS. Coefficients can change but subscripts can't.
4.) numbers of atoms on both sides of the equation are balanced