Balancing Equations

Balancing, Writing, and Naming Equations

Warm Up 10/2

Please get your Science Scoring Log out and be prepared to update it (on back of Unit 1 Packet)

Cross off 1-E1 from Assignment list and add Law of Conservation of Mass Lab in its place.

Balancing Equations

Balancing Equations Law of Conservation

of Matter: In a chemical reaction,

matter can be neither created nor destroyed.

In a chemical reaction, the amount of reactants equals the amount of products.

Balancing Equations Also known as: Law of Conservation

of Atoms: The number of atoms

of each type of element must be the same on each side of the equation.

Balancing Equations

Hydrogen and oxygen are diatomic elements (won’t exist alone!).

Their subscripts cannot be changed. The subscripts on water cannot be

changed. Can only add coefficients until

balanced

Hydrogen + oxygen water

H2 + O2 H2O

Balancing Equation Steps 1. First, identify the reactant side and

the product side. 2. Draw a line coming down from the

yield sign (arrow) 3. List the elements on each side of

the arrow4. Count the elements on each side of

the arrow5. Begin balancing (might have to go

back and forth a few times until everything is balanced!)

Balancing Equation Steps

1. Count the atoms on each side and ALWAYS write it out like this:

Reactant Side Product Side H=2 H=2 O=2 O=1

H2 + O2 H2O

Balancing Equations

H2 + O2 H2O

If the subscripts cannot be altered, how can the atoms be made equal?

Adjust the number of molecules by changing the coefficients.

Balancing Equations

Reactant Side Product Side H=2 H=4 O=2 O=2

H is no longer balanced.

H2 + O2 2H2O

Balancing Equations

Reactant Side Product Side H=4 H=4 O=2 O=2

It is now balanced because the proper amounts of coefficients were added!

2H2 + O2 2H2O

Balancing Equations

Reactant Side Product Side N=2 N=1 H=2 H=3

N2 + H2 NH3

Nitrogen + hydrogen ammonia

Balancing Equations Nothing is balanced. Balance the nitrogen first by

placing a coefficient of 2 in front of the NH3.N2 + H2 2NH3

Reactant Side Product Side N=2 N=1 2H=2 H=3 6

Balancing Equations Hydrogen is not balanced. Place a 3 in front of H2

N2 + 3H2 2NH3

Reactant Side Product Side N=2 N=1 2

H=2 6 H=3 6

What about Polyatomic Ions?

-Follow the same steps as normal EXCEPT, do NOT break apart the polyatomic ions!

Reactant Side Product Side

Ca= 3 Ca= 1 PO4= 2 PO4= 1

H= 2 H= 3 SO4= 1 SO4= 1

Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4

Balancing Equations

Balance the metal first by placing a coefficient of 3 in front of CaSO4.

Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4

Ca3(PO4)2 + H2SO4 3CaSO4 + H3PO4

Reactant Side Product Side Ca= 3 Ca= 1 3

PO4= 2 PO4= 1

H= 2 H= 3 SO4= 1 SO4= 1 3

Balancing Equations Next, balance the ion groups Last, balance the rest of the atoms

Ca3(PO4)2 + 3H2SO4 3CaSO4 + H3PO4 3 sulfate groups are needed on the

reactant side so place a coefficient of 3 in front of H2SO4.

Balancing Equations

Reactant Side Product Side Ca= 3 Ca= 1 3

PO4= 2 PO4= 1

H= 2 6 H= 3 SO4= 1 3 SO4= 1 3

Ca3(PO4)2 + 3H2SO4 3CaSO4 + H3PO4

Neither H nor PO4 is balanced!

Balancing Equations A coefficient of 2 placed in front

of H3PO4 balances both hydrogen and phosphate.

Ca3(PO4)2 + 3H2SO4 3CaSO4 + 2H3PO4

Congratulations! You are now finished!!!