Transcript Balance Equations - Solon City Schools

BALANCING CHEMICAL
EQUATIONS
A BALANCED EQUATION
• Atoms cant be created or destroyed
• Law of Conservation of Mass
• All the atoms we start with we must
end up with
• A balanced equation has the same
number of each element on both
sides of the equation (reactant and
product sides).
COUNTING ATOMS
•
2H2 + O2 
• Reactants
2H2O
 Product
• Subscript: (numbers below)
• indicates how many atoms of an
element.
• Coefficient (numbers in front)
• Indicates how many molecules of a
compound
• (multiplies the number of atoms of
each element in the compound)
Chemical Formula
Counting up Atoms
Let’s Practice
• NH3
1
• _____
3
• _____
1
• _____
• NaCl
1
• _____
1
• _____
1
• _____
atoms of Nitrogen
atoms of Hydrogen
molecules/moles of NH3
atoms of Sodium
atoms of Chlorine
molecule/moles of NaCl
PRACTICE AGAIN
• 8NaCl
8 atoms of Sodium
• _____
8 atoms of Chlorine
• _____
8 molecule/moles of NaCl
• _____
• 3NH3
• ____
3 atoms of Nitrogen
9 atoms of Hydrogen
• ____
3 molecule/moles of NH3
• ____
• Ca(NO3)2
1 atoms of Calcium
• _____
2 atoms of Nitrogen
• _____
6 atoms of Oxygen
• _____
1 molecule/moles of Ca(NO3)2
• _____
RULES FOR BALANCING
 Write the correct formulas for all the
reactants and products
 Count the number of atoms of each
type appearing on both sides
 Balance the elements (make them
same amount on reactant and
product sides) one at a time by
adding coefficients (the numbers in
front).
 Check to make sure it is balanced.
NEVER!
• Change a subscript to balance an
equation.
• If you change the formula you are
describing a different reaction.
• H2O is a different compound than
H2O2
• Never put a coefficient in the middle
of a formula
• 2 NaCl is okay, Na2Cl is not.
EXAMPLE
H2 + O2  H2O
Make a table to keep track of
where you are
EXAMPLES
• CH4 + O2  CO2 + H2O
• AgNO3 + Cu  Cu(NO3)2 + Ag
• Mg + N2  Mg3N2
• P + O2  P4O10
• Na + H2O  H2 + NaOH
ANSWERS TO EXAMPLES
• CH4 + 2O2  CO2 + 2H2O
• 2AgNO3 + Cu  Cu(NO3)2 + 2Ag
• 3Mg + N2  Mg3N2
• 4P + 5O2  P4O10
• 2Na + 2H2O  H2 + 2NaOH