On the sides of reactants and products, a balanced chemical equation contains an equal amount of atoms of various elements. In an imbalanced chemical equation, the reaction contains an uneven amount of atoms of one or more elements. An imbalanced chemical equation can be either acid or base.
In chemistry, acids are substances that donate hydrogen ions (H+), bases are substances that accept them. Acids and bases can be further divided into strong and weak acids/bases. Strong acids have a pKa less than 7, while strong bases have a pKa greater than 14. Most chemicals fall in this range and are referred to as moderate acids or bases.
Acids and bases can change other molecules to create new compounds. For example, hydrochloric acid changes sugar molecules to create cellulose and water. Base-catalyzed reactions are important in organic synthesis. The presence of bases can promote hydrolysis reactions, ring openings, and other processes that would not otherwise occur quickly at neutral pH. Bases can also inhibit some reactions through ionization of certain reactive centers. Inorganic acids and bases include HCl, H2SO4, NaOH, and KOH. Organic acids and bases include CH3COOH, HCOOH, C6H5OOCCH3, and NH3.
A chemical equation is said to be balanced when the number of various atoms of elements on the reactant side equals the number of atoms on the product side. Balancing chemical equations is a trial-and-error procedure. The quantities of the reactants and products must be modified to balance the equation.
For example, if we were to balance the chemical equation for water vapor:
H2O (s) + 2NaOH (aq) → 2Na+ (aq) + H2 (g) + OH− (aq)
We would get 1.5 moles of sodium hydroxide and 0.5 mole of hydrogen gas need to be reacted with one mole of water to yield two moles of sodium hydroxide and one mole of hydrogen gas. There are also 0.5 moles of water in the original mixture so there should be two moles of water in the final mixture.
This shows that the equation is not balanced because there are more hydroxide ions than water molecules in the final mixture. Hydroxide ions are produced from the sodium hydroxide while water molecules are produced from the water vapor. Therefore, we need to add more water vapor to the reaction system to achieve equilibrium.
Balanced Chemical Equations for Kids: Examples
Sodium carbonate is formed by the addition of acid to soda.
When an element has an equal number of atoms on both sides of a chemical equation, the equation is balanced. Atoms do not disappear or appear; they are always present in equal numbers. Elements that can be used up or lost through radioactive decay are called non-balancing elements.
Elements that balance all chemical equations are called balancing elements. The hydrogen and the oxygen in water are examples of balancing elements. They cannot be used up or lost because their numbers are always the same as the numbers of atoms in the water molecule.
Non-balancing elements can be either positive or negative ions. For example, the carbon atom in CO2 is a non-balancing negative ion. It loses two electrons and becomes CO+. At the same time, it gains two protons from its neighboring hydrogen atoms and becomes H2O. Carbon is a balancing element because it has an equal number of electrons and protons. It does not matter which form it takes; carbon is carbon.
Elements that have more atoms than there are particles in the universe are called inert gases. For example, there are twice as many nitrogen atoms as there are nucleons (protons and neutrons) in the universe.