Atom Inventory

Notes and Pictures

How many atoms of each element are there on each side of the of the

equation?

What should be true about the number of atoms if conservation

occurs?

Balanced Equation

• Shows a chemical reaction

• Shows the specific compounds that interact

• Shows the new compounds created

• Shows that matter is conserved, because the number of atoms of each element involved is the same before and after the reaction

What does the equation show?

• A chemical reaction

• How different compounds chemically react with each other to form new compounds

• The compounds on the left (present at the start of the reaction) are called Reagents

• The compounds on the right (present at the end of the reaction) are called Products

To balance an equation• Change only coefficients, not formulas

• Start with elements appearing only once on each side

• Balance the H’s and O’s generally last

• Double check to make sure each side of the equation has got the same number of atoms for each element

How about this reaction?

• 2Ca (s) + O2 (g) 2CaO (s)

• How does the 2 in front of the CaO differ from the subscript after O?

• Does this represent matter that is conserved?

• Is the equation Balanced?

Balanced equation

• A reaction equation whose Reagent and Product sides have the same number of atoms of each element involved

• Like a math equation, each side has the same overall amount

Balancing equations

• For the equations to show conservation, they must be balanced

• Change Coefficients before each compound to balance the number of atoms of each element to be the same on both sides of the equation

• Do NOT change the subscripts

Notes on balanced equation• Water will be written into the equation only if it

is broken up or created

• Just because a compound is in an aqueous solution does not mean water is an active ingredient

• The quantity of a compound needed for the chemical reaction is proportional to the coefficient in front of the compound