Chemical Equations

Chemical Equations

Chemical equation - a chemical “sentence” that describes change, using numbers, symbols, and chemical formulas

• A chemical equation can help you predict what you will observe when the reactants are combined
• Chemical equations describe chemical reactions

Reactants ---------------------------------------------------------------------------------------------------------------> Products

The starting materials of a chemical rxn                “yields"                                                             New substance that is formed
Go through a chemical rxn                                        indicates the chemical rxn                           Listed on the right
Listed on the left

Example:

H₂(g) + Cl₂(g) -----> 2HCl(aq)

• The subscripts show how many of each atom
• The coefficient shows how many of each molecule
• (s)- solid, (g)- gas, (aq)- aqueous, (l)- liquid-- show the state of matter

Law of Conservation of Mass:

Matter can be neither created nor destroyed in physical and chemical changes. Matter is conserved. Individual atoms are conserved in chemical reactions and physical changes, so the number of atoms remains the same from start to finish. Mass is also conserved, so the total mass of the products is equal to the mass of the reactants. 

4 Steps for Balancing Equations:

1. Get the skeleton equation
2. Draw boxes around the chemical formulas
3. Make an element inventory
4. Update your inventory until balanced

(# atoms of reactants = # atoms of products)