November 30, 2011
Balancing Chemical Equations
There are two sides to a chemical equation, the
reactant side and the product side.
reactants

products
· Note the direction of the yield arrow
H2 + O 2

Reactant side
H2 + O2
Product side
H 2O
Product side

H 2O
Reactant side
created by Donna Cowan Marcelo
November 30, 2011
Balancing Chemical Equations
All the elements on one side of the chemical equation are
also on the other side of the equation. Elements cannot
appear or disappear. A chemical equation simply shows
that elements break, build and/or switch bonds during a
chemical reaction.
(note: these equations are not balanced)
S 8 + O2

SO3
This equation is correct as it has Sulfur and Oxygen on
both sides.
Zn + 2HCl  2Cl + Zn
This equation is incorrect because Hydrogen, which is on
the reactant side of the equation, has disappeared from the
product side of the equation
KClO3 KCl + O2 + S
This equation is incorrect because Sulfur, which is not on
the reactant side of the equation, has appeared on the
product side of the equation
created by Donna Cowan Marcelo
November 30, 2011
Balancing Chemical Equations
· Look at the following equation.
· Find the color that you need to balance.
· Touch and drag the matching molecule from the box and
place it under its corresponding molecular formula.
· Remember, you may only drag reactant molecules to the
reactant side and product molecules to the product side.
· After balancing the equations by dragging and dropping
the molecules under their proper place, count the number
of molecules (including the original one under the
formula) and write that number, called the coefficient, in
front of the molecule in that equation. If the coefficient is
one (1) you may leave it blank - the number one being
understood.
· Your equation is balanced. You should check to see
whether your coefficients are in simplest form.
The following page demonstrates how to use this tool. Press
play to observe or skip this page and go on to the next to
balance those equations.
created by Donna Cowan Marcelo
November 30, 2011
Demonstration Page
Press play at the bottom.
__KBr + __Cl2 => __KCl + __Br 2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
__ P + __ O 2 __P2O5
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ NaBr + ____ CaF2  ____ NaF + ____ CaBr2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
__FeCl3 + __ NaOH  __ Fe(OH)3 + __ NaCl
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ Pb(OH)2 + ___ HCl  ___ H2 O
box of reactant
molecules
+ ___ PbCl2
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ N2 + ____ H2  ____ NH3
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ CH 4 + ____ O 2
box of reactant
molecules
 ____ CO 2 + ____ H 2O
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ C3H8 + ____ O2  ____ CO2 + ____ H2O
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ S8 + ___
box of reactant
molecules
O2  ___
SO3
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ HCl + ____ CaCO3  ____ CaCl2 + ____H2O + ____ CO2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ KClO3  ____ KCl + ____ O2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ AlBr 3 + ____ K2SO4  ____ KBr + ____ Al2(SO4)3
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ H2O + ____ O2  ____ H2O2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ Ag2 O
 ___ Ag + ___ O2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
____ K + ____ MgBr  ____ KBr + ____ Mg
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___CO 2 +___NH3  ___OC(NH 2)2 + ___H2O
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___HgO

box of reactant
molecules
___ Hg + ___O 2
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
__ C7H6O 2 +
__ O 2

__ CO 2 + __ H 2O

box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
_____ FeS2 + _____ O2
box of reactant
molecules

_____ Fe2O3 + _____ SO2
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ SiCl4 +____ H2O
box of reactant
molecules
 ___ H4SiO4 + ___ HCl
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ V2O5 + ___ CaS  ___ CaO + ___ V2S5
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ Mn(NO2)2 + ___ BeCl2  ___ Be(NO2)2 + ___ MnCl2
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___ AgBr + ___ GaPO4  ___ Ag3PO4 + ___ GaBr3
box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
___NH3 + ___NO
box of reactant
molecules

___N2 + ___H2O
box of product
molecules
created by Donna Cowan Marcelo
November 30, 2011
Try your own equation. Use the shape tool to make the atoms. Select
the colors. Form the molecules by highlighting all of them and
grouping them. Drag and drop them into the proper box. Make them
infinite cloners and you are good to go!

box of reactant
molecules
box of product
molecules
created by Donna Cowan Marcelo