  Chemical Equations tutorial

A chemical equation is a short hand expression of a chemical reaction. There are two parts to a chemical equation. The reactants are the elements or compounds on the left side of the arrow (-->). The elements and compounds to the right of the arrow are the products. Identify the reactants and the products in the equation below. Reactants: 2 H2 + O2
Products: 2H2O

Look at the equation above. Notice the two purple 2s. These numbers are called coefficients. Coefficients are used to balance chemical equations.

The blue arrow is a yield sign. It separates the reactants form the products. Most yield signs will be like the one above, but there are some other yield signs you need to know. A formula written above a yield sign indicates it is a catalyst used to speed up a reaction. A triangle above the yield sign indicates the reaction is heated. Two half arrows pointing in opposite directions indicates that this is a reversible reaction.

The following symbols are written in parenthesis after a formula and represent the state of the element or compound.

 s solid solid precipitate is produced (used for products only, not reactants) cr crystalline (used for solid ionic compounds) l liquid aq aqueous (substance is dissolved in water) g gas gas is produced (used for products only, not reactants)

Identify the following about the equation below: the reactants, the products, the coefficients used, the state of each element or compound. Reactants: 2 Na (s) + 2H2O (l)
Products: 2 NaOH (aq) + H2 Coefficients: 2,2,2
State:
Na - solid, H2O - liquid, NaOH - aqueous, H2 - gas