Steps In Balancing A Chemical Equation

A chemical equation is symbolic representation of a chemical reaction where the reactant entities are given on the left hand side and the product entities on the right hand side. The coefficients next to the symbols and formulae of entities are the absolute values of the stoichiometric numbers. The first chemical equation was diagrammed by Jean Beguin in 1615.

Form

A chemical equation consists of the chemical formulas of the reactants, the starting substances, and the chemical formula of the products, substances formed in the chemical reaction. The two are separated by an \rightarrow —usually read as "yields"— and each chemical formula is separated from others by a plus sign.

As an example, the formula for the burning of methane can be denoted:

CH|4| 2 O|2| \rightarrow CO|2| 2 H|2|O

This equation would be read as "CH four plus O two yields CO two and H two O." But for equations involving complex chemicals, rather than reading the letter and its subscript, the chemical formulas are read using IUPAC nomenclature. Using IUPAC nomenclature, this equation would be read as "methane plus oxygen yields carbon dioxide and water."

This equation indicates that oxygen and CH ₄ react to form H ₂ O and CO ₂ . It also indicates that two oxygen molecules are required for every methane molecule and the reaction will form two water molecules and one carbon dioxide molecule for every methane and two oxygen molecules that react. The stoichiometric coefficients, the numbers in front of the chemical formulas, result from the law of conservation of mass and the law of conservation of charge (see "Balancing Chemical Equation" section below for more information).

Common symbols

Symbols are used to differentiate between different types of reactions. To denote the type of reaction:

• "=" symbol is used to denote a stoichiometric relation.
• "\rightarrow" symbol is used to denote a net forward reaction.
• "\rightleftarrows" symbol is used to denote a reaction in both directions.
• "\rightleftharpoons" symbol is used to denote an equilibrium.

Physical state of chemicals is also very commonly stated in parentheses after the chemical symbol, especially for ionic reactions. When stating physical state, (s) denotes a solid, (l) denotes a liquid, (g) denotes a gas and (aq) denotes an aqueous solution.

If the reaction requires energy, it is indicated above the arrow. A capital Greek letter delta, \Delta, is put on the reaction arrow to show that energy in the form of heat is added to the reaction. h\nu is used if the energy is added in the form of light.

Balancing chemical equations

The law of conservation of mass dictates the quantity of each element does not change in a chemical reaction. Thus, each side of the chemical equation must represent the same quantity of any particular element. Similarly, the charge is conserved in a chemical reaction. Therefore, the same charge must be present on both sides of the balanced equation.

One balances a chemical equation by changing the scalar number for each chemical formula. Simple chemical equations can be balanced by inspection, that is, by trial and error. Another technique involves solving a system of linear equations ...