Chemical equations

What are chemical equations? A short, easy way to show a chemical reaction. Chemical equations use chemical formulas and other symbols instead of words to summarize a reaction.

Parts of a Chemical Equation REACTANTS are on the LEFT and PRODUCTS are on the RIGHT

Count the atoms in the Chemical Equation Count the number of atoms for each element on both sides Ca = ___ C = ___ O = ___ Ca = ___ C = ___ O = ___

Count the atoms in the Chemical Equation Count the number of atoms for each element on both sides Ca = _1_ C = _1_ O = _3_ Ca = _1_ C = _1_ O = _3_

Count the atoms in the Chemical Equation Ca = _1_ C = _1_ O = _3_ Ca = _1_ C = _1_ O = _3_ Is the chemical equation balanced? YES, there are the same number of atoms for each element on both sides.

Why does a chemical equation need to be balanced? The Law of Conservation of Mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products. *Remember… Matter cannot be created nor destroyed!

Is this equation balanced? Let’s count the atoms to find out… H2 + O2  H2O H = H = O = O =

Is this equation balanced? Let’s count the atoms to find out… H2 + O2  H2O H = 2 H = 2 O = 2 O = 1 NO!

How can we balance the equation? The only thing we can do to balance a chemical equation is to ADD COEFFICIENTS. Coefficients increase the number of atoms. They multiply through the symbol/formula. *You CANNOT change the subscripts! H = 4 H = 4 O = 2 O = 2

We need to add coefficients to balance the equation. 2 H2 + O2  2 H2O H2 + O2  H2O This equation is NOT balanced! There are more oxygen atoms on the left.

Practice example This equation is not balanced… Count the atoms. __ Na + __ Cl2  __ NaCl Na = 1 Na = 1 Cl = 2 Cl = 1

Balancing chemical equations Add Coefficients… __ Na + __ Cl2  2 (NaCl) Na = 1 Na = 2 Cl = 2 Cl = 2

Balancing chemical equations Add Coefficients… 2 (Na) + __ Cl2  2 (NaCl) Na = 2 Na = 2 Cl = 2 Cl = 2 Balanced!