Chemical Equations to Balance

What is a Chemical Equation?

A chemical equation, also known as a chemical formula, is a written representation of numbers and symbols that denotes a process and production of a chemical reaction. It is a composition of both reactants and products, separated by an arrow (chemical reaction arrow), which indicates that a chemical reaction is occurring. Reactants are written on the left side of the arrow while the products are located on the right side.  An example of a simple chemical equation looks like this:

2 H2+ O2 → 2 H2O

Their symbols represent the elements in the chemical equation (which are the H = Hydrogen and O = Oxygen) in the periodic table. The coefficient located next to the symbols (the “2” before “H” from 2 H2) indicates the stoichiometric numbers. In contrast, the subscripts (the small “2” located after “H” and “O”) represents the number of atoms present in a chemical species. The example above shows that 2 H+ Oare the reactants, while 2 H2O is the product of the reaction.


Types of Chemical Reactions

Chemical reaction, which was developed by Antoine Lavoisier, takes place when two or more molecules interact with one another and produce a new product through chemical change. This may include atoms, ions, compounds, along with molecules of a single element to perform the reaction. Some chemical reactions may either a forward or reverse reaction to obtain the desired product. There are various types of chemical reactions and some of them are:

Direct Combination or Synthesis Reaction

During a synthesis reaction, two or more elements mix to produce a new product.This type of reaction is one of the most common types of reaction that follows a simple formula of A + B → AB and is the reverse of the decomposition reaction. One way to recognize this reaction is that this has more reactants than its products. Some good examples of synthesis reactions are the production of water (H2O), carbon dioxide (CO2), and ammonia (NH3). The chemical equation for a synthesis reaction may look like this:

2 H2 (g) + O2 (g) → 2 H2O (g)
Chemical Decomposition or Analysis Reaction

In reverse to the synthesis reaction, chemical decomposition breaks compounds into smaller chemical species as its product, following the formula of AB → A + B. The extraction of various metals, the digestion of food, and the electrolysis of water (H2O) into oxygen (O2) are good examples of chemical decomposition. The chemical equation of a chemical decomposition may look like this:

2 H2O (g) → 2 H2 (g) + O
Single Displacement or Substitution Reaction

The substitution reaction occurs by displacing one element to another element to form a new compound. The starting materials are always made from pure elements like hydrogen (H) and zinc (Zn), which are added to an aqueous compound such as saltwater and acid solutions. This type of reaction follows an A + BC → B + AC formula and is crucial for the production of pharmaceutical, agrochemical, and industrial products. The chemical equation of a substitution reaction may look like this:

2 K + 2 H2O → 2 KOH + H2
Metathesis or Double Displacement Reaction

Like the single displacement reaction, metathesis also displaces elements from a compound to another element. However, unlike the single displacement reaction, two compounds (reactants) exchange bonds (either covalent or ionic) to form a new compound (product) called precipitate in metathesis. Furthermore, this type of reaction follows an AB + CD → AD + CB formula, producing either a precipitation reaction and neutralization reaction as a result. An example of a metathesis reaction is the combination of milk and baking powder in a recipe. The chemical equation of a metathesis reaction may look like this:

NaCl (aq) + AgNO (aq) → AgCl (s) + NaNO(aq)
Combustion Reaction

A combustion reaction is a type of redox reaction that focuses on forming oxidized products and generating heat by combining a combustible reactant with an oxidizer. Oxygen (O2) plays a crucial role in this type of reaction as the substance must react with oxygen gas to release energy and form light and heat as its product. Hence, requiring oxygen to be part of the reactants. A good example of a combustion reaction is the burning of a wax candle or the combustion of methane. Furthermore, the chemical equation of a combustion reaction may look like this:

CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
Oxidation-Reduction or Redox Reaction

The number of atoms changes during a redox reaction, wherein electrons transfer from one chemical species to another in the process. A good example of a redox reaction is the corrosion of metal, the decomposition of organic matter, and the process of photosynthesis that takes place in the leaves of a plant. The chemical equation of a redox reaction may look like this:

2 S2O32-(aq) + I2 (aq) → S4O62-(aq) + 2 I(aq)
Acid-Base Reaction

An acid-base reaction is a different kind of double displacement reaction between acids and bases, exchanging more than one hydrogen ions H+ between chemical species, both neutral (water and acetic acid) or electrically charged ions  (ammonium, hydroxide, and carbonate), during the process.A good example of this type of reaction is the combination of vinegar (acid) and baking soda (base), which neutralizes the acid and base substances to yield salt (NaCl) and water (H2O). The chemical equation of an acid-base reaction may look like this:

HCl + KOH → KCl + H2O

Hydrolysis Reaction

If combustion reaction requires oxygen to form a new product, hydrolysis reaction, from the term “hydro” (water) and “lysis” (to break apart), requires water to react. This is a type of decomposition reaction where water acts as a reactant to break chemical bonds in other reactants and is considered to be a reverse condensation reaction. An example of a hydrolysis reaction is the combination of sodium acetate (a type of salt) with water to form acetic acid. The chemical equation of a hydrolysis reaction may look like this:

AB + H2O → AH + BOH

Basic Rules for Writing a Chemical Equation

Writing a chemical equation is like baking a cake. Why? Because baking requires ingredients and a specific recipe to produce its desired product. Similarly, in Chemistry, writing a chemical equation and balancing it requires elements, compounds, and atoms to interact with one another to form a new product. Plus, chemical equations follow a particular procedure to achieve its desired outcome. Learn more about writing and balancing chemical equations with this few basic rules: 

How to Balance a Chemical Equation?

Balancing a chemical equation does not have a particular ruling; instead, it is a process of trial and error until every element present within the equation is balanced. When chemical equations are balanced, the law of conservation of matter is satisfied, which shows that matter is neither created nor destroyed. Acquire the basic knowledge in balancing chemical equations by following these few steps below.

Step 1: Write Down the Chemical Equation

Begin by writing down the chemical equation on a piece of paper. Break each molecule into individual atoms, then count the number of atoms present in the equation. Do this by calculating the value of the subscripts and coefficient of each molecule (both reactants and products). 

Step 2: Begin Balancing the Single Elements

To make things easier, save the elements that are found on both sides of the equation for last to avoid redundancy in calculating. Start balancing the equation with the element that has a single molecule, whether it’s located in the reactant’s side of the product’s side. Using the element’s coefficient, add it to the same element situated on the other side to equalize the number of atoms present in both elements. Adjust the other element’s values to balance everything. 

Step 3: Balance the Remaining Complex Substances

Now, it’s time to move onto the more complex compounds. Balance the remaining atoms, if a fractional coefficient is present, multiply both sides of the equation by the denominator to obtain whole numbers for the coefficients. Make sure that the total value of subscripts and the coefficient balances the other element located on the other side. 

Step 4: Count the Number of Atoms on Both Sides

Lastly and most importantly, before anything else, make sure to review the chemical equation. Count the number of atoms for each element on both sides and see to it that each element has the same total amount of atoms. If all elements are balanced, the entire equation is balanced.



What are the basic symbols used in writing a chemical equation?

  • +      : separates various reactants and  products
  • →    :the yield sign that separates reactants and products
  • ⇋    : reversible reactions that achieve the equilibrium
  • (s)   : solid state reactant or product
  • (l)    : liquid state reactant or product
  • (g)   : gas state reactant or product
  • (aq) : aqueous state reactant or product

Why do you balance a chemical equation?

The law of conservation of matter, like any other law, explains a large number of observations in science. The law of conservation, in particular, provides the foundation in chemistry because it demonstrates that matter stays constant regardless of how much it’s transferred. Hence, chemical equations are balanced to satisfy this law.

How do you know if a chemical equation is balanced?

Once the total amount of atoms on each element, both reactants, and products, has the same value on the opposite side, the chemical equation is considered to be balanced.

What happens if chemical equations are not balanced?

A chemical equation is not balanced when both sides of the equation have an unequal amount of atoms. According to the law of conservation of matter, “matter can neither be created nor destroyed.” When the equation is not balanced, this indicates that mass has been created or destroyed, which contradicts the law of conservation of matter.

What is chemical equilibrium?

Chemical equilibrium is the state when a chemical reaction fails to convert all its reactants to products, in which the concentrations of the reactant and product are unchanging over time due to the same rate of forward and backward reaction. This means that the response reaches a dynamic equilibrium wherein both reactants and products are present. However, this does not necessarily require both reactants and products to be present in equal amounts.

As a recap, chemical reactions occur every day. Scientists, studies and identifies chemical reactions by writing their chemical equations. A chemical equation is represented by numbers and symbols that denote the process and production of a chemical reaction. As stated earlier, there are various types of chemical reactions that occur in the environment. These reactions are beneficial to humanity as they help them understand the properties of matter, allowing them to produce essential products, solve crimes, innovate technology, and, most of all, develop their way of living.