BALANCING CHEMICAL REACTIONS: A TUTORIAL

By: Jennifer Kocan & Hunter Edwards

What is a Chemical Reaction? A chemical reaction is a change in which

two or more substances combine to form a new substance or substances.

http://dev-school.discoveryeducation.com/curriculumcenter/chemistry/glossary.html

The two or more products you begin with are called reactants.

The new substance(s) formed are called products.

For example, when the acetic acid in vinegar and baking soda (reactants) are combined, the products are bubbles of carbon dioxide gas, water, and sodium acetate.

http://www.enotes.com/science-experiments-projects/chemical-properties/

The Law of Conservation of Mass “A relation stating that in a chemical

reaction, the mass of the products equals the mass of the reactants.”

http://chemistry.about.com/library/glossary/bldef5660.htm

This means when a chemical reaction occurs, the products and reactants will have the same mass.

Why is it Important to Balance Chemical Reactions? Balanced chemical equations obey the

Law of Conservation of Matter and are true representations of what actually occurs in nature.

http://galileo.phys.virginia.edu/education/outreach/8thgradesol/ConservMatter.htm

Remember- A chemical equation is a shorthand method for describing a chemical change.

http://microship.com/resources/resourcepix/cgdb-1.jpg

Step 1

To start, place reactants on the left-hand side of the equation.

Products go on the right hand side of the equation.

Remember- The law of conservation of mass states that matter is neither created or destroyed, so all the atoms in the reactants must end up somewhere among the products.

Example (Step 1)

Here you have an unbalanced equation.

K + Br2 KBr

Step 2

Count the number of atoms of each element, compound or ion in the reactants and products.

http://facstaff.gpc.edu/~pgore/PhysicalScience/atom-with-electrons.gif

Example (Step 2)

Count the number of atoms of each element.

1 21 1

K + Br2 KBr

*Make sure you understand that you must have 2 atoms of Bromine on the right side of the equation, since there are 2 atoms of Bromine on the left side.

Step 3

Remember- numbers appearing in the formula below an element are known as subscripts. These can never be changed when balancing the equation or you will change the entire equation.

http://chemistrygeek.com/balance1.htm

Step 4

Balance the atoms one at a time by putting coefficients (simple, whole numbers written in front of chemical formulas) in front of the formula, so that the numbers of atoms of each element are equal on both sides of the equation.

This means that if you have atoms A2 and B2 on one side of the equation, you must have A2 and B2 on the other side (equal number of atoms).

www.bcs.whfreeman.com/practiceofchemistry//cat_080/gloss.htm

Example (Step 4)

Balance: Two 2’s were placed in the underlined spots so the number of atoms of Bromine are equal.

2K + Br2 2KBr•2 times K is 2 K (Two atoms of Potassium)•2 atoms of Bromine•2 times K and Br is two atoms of Potassium and two

atoms of Bromine

Step 5

Make sure all the coefficients are in the smallest possible whole number ratio (simplify).

Example: 4 and 6 are simplified to 2 and 3.

Basically all you’re doing when your balancing a chemical reaction equation is making sure that each side of the equation has the same number of atoms as the other side does.

Example (Step 5)

Here is the complete balanced equation.

2K + Br2 2KBr

Try This!

C5H12 + O2 -----> CO2 + H2O

Bibliography

Chemistrty Ciriculum center- http://dev-school.discoveryeducation.com/curriculumcenter/chemistry/glossary.html

Chemistry 1: Balancing Equations http://chemistrygeek.com/balance1.htmconservation

Conservation of matter and balancing equations http://galileo.phys.virginia.edu/education/outreach/8thgradesol/ConservMatter.htm

www.bcs.whfreeman.com/practiceofchemistry//cat_080/gloss.htm