jlk009 balancing chemical reactions

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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.

   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.
The Law of Conservation of Mass
   “A relation stating that in a chemical reaction, the
    mass of the products equals the mass of the

   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.

       Remember- A chemical equation is a shorthand
        method for describing a chemical change.
Step 1
   To start, place reactants on the left-hand side of the
   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.
Example (Step 2)
   Count the number of atoms of each element.

                            K + Br2  KBr
                        1                       1    1

    *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.

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
   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).
   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
   Chemistrty Ciriculum center-

   Chemistry 1: Balancing Equations

   Conservation of matter and balancing equations


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