Chemistry Reaction

Consider a chemistry reaction (chemical reactions) as an equation. Basically, the starting materials react to make a product(s). In the chemical equation, the reactants (starting materials) are separated from the products by an arrow. On the left side of the arrow are the reactants, while the right side of the arrow has products.

Note: there can also be two reversible arrows indicating that the reaction is reversible.

Types of Chemical Reactions

There are five general types of reactions: combination, decomposition, single-replacement, double-replacement and combustion.

In a combination reaction, there will always be a single product.
In a decomposition reaction, a single compound is broken down into two or more simpler substances.
In a single-replacement reaction, both the products and the reactants are an element and a compound.
A double-replacement reaction generally takes place between two ionic compounds in aqueous solution.
A combustion reaction always involves oxygen as a starting material (reactant).

In chemical reactions, it is important to have balanced equations

Rules for Writing/Balancing Equations:

You should determine the correct formulas for all the reactants and products
Write a simple equation by placing the formulas for the reactants on the left side and the formulas for the products on the right side with a yield sign (–––>) in between. When two or more reactants or products are involved, you need to separate their formulas with plus signs.
Then determine the number of atoms of each element in the reactants and products. Count a polyatomic ion as a single unit if it appears unchanged on both sides of the equation.
Balance the elements one by one using coefficients. When no coefficient is written, it is assumed to be 1. Start by balancing elements that appear only once on each side of the equation. Never balance an equation by changing the subscripts in a chemical formula.
Check each atom or polyatomic ion to be sure they are equal on both sides of the equation
Make sure all the coefficients are in the lowest or simplified ratio.

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