Information Displayed in a Chemical Reaction Equation

What information is included in a chemical reaction equation?



B11.5 Writing out a chemical reaction equation
Chemical reaction equations display a lot of information. Understanding how to interpret that information is key to your success in this section.

Entities (elements and compounds) that are written on the left-hand side of the arrow are the reactants; these are what you start with in a chemical reaction.

Entities written on the right-hand side of the arrow are the products; these are what you end up with once the reaction goes to completion.

Numbers in front of formulas are coefficients, and these are used to balance the reaction. This is to ensure that there are the same number of atoms of each type of element on the reactant side and the product side.

States are indicated in brackets behind each entity’s formula. Please note that since your textbook was written, standards have changed and states are no longer written as subscripts. The states used are

(s)—solid
(l)—liquid
(g)—gas
(aq)—aqueous

Aqueous means a solution; the indicated compound has been dissolved in water to produce a solution.





  Read This

Please read pages 86 to 88 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on how to properly write chemical reaction equations. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions

Complete the following practice question to check your understanding of the concept you just learned. Make sure you write a complete answer to the practice question in your notes. After you have checked your answer, make corrections to your response (where necessary) to study from.

  1. List four pieces of information provided by a balanced chemical reaction equation.

    A balanced chemical reaction equation provides
    1. the formulas of the reactants
    2. the formulas of the products
    3. the states of the reactants and products
    4. the number of molecules of the reactants and products
  2. Use the following chemical reaction equation to explain the following terms: reactants, products, state, and coefficient.

    2KClO3(s) → 2KCl(s) + 3O2(g)

    reactant—KClO3(s)
    products—KCl(s) and O2(g)
    states—KCl and KClO3 are both solids (s) and O2 is a gas (g)
    coefficients—KCl and KClO3 both have a 2 as the coefficient, whereas O2 has a 3