Loading chem110..

In the upcoming lessons we’re going to begin to explore chemical reactions. During a chemical reaction, bonds and lone pairs are redistributed among the substances involved in the reaction. In order words, bonds are broken and formed during reactions, and electrons are rearranged among the structures of the reactants.

Mass is conserved during chemical reactions, meaning that no matter is created or destroyed during the reaction. The identities of all atoms involved remain the same (i.e., the nuclei do not change during a chemical reaction). Therefore, the number of atoms of each element involved in the reaction must be equal in both the products and reactants.

Chemical reactions can be described using a reaction equation like the one presented in Figure 1. The reaction equation identifies the reactants (on the left side of the arrow) and the products of the reaction (on the right side of the arrow). Each molecular formula in the reaction equation is preceded by a coefficient that identifies the number of moles of each substance that are involved in the reaction. For example, the combustion of ethane involves the reaction of two moles of ethane ( C_2H_6 ) with seven moles of oxygen to produce four moles of carbon dioxide and six moles of water, as shown in the reaction equation. If no coefficient is shown in front of a molecular formula then the coefficient is assumed to be one. This equation is said to be balanced because the same number of each type of element appears on both sides of the reaction equation. Notice that there are 4 carbon atoms, 12 hydrogen atoms, and 14 oxygen atoms on both the reactant (left) and product (right) sides of the reaction equation.