Download 3.3 How do we balance equations

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3.3 How do we balance equations?
Date:_____________
ADPHS Instructor Ms. Kasia Rm 109
Unit 2 Chemical Reactions
3.3 How do we balance equations?
AIM:
DO NOW: MR #3 An element that has a low first ionization energy and good conductivity of heat and
electricity is classified as a
(1) metal
(3) nonmetal
(2) metalloid
(4) noble gas
HOW DO WE BALANCE EQUATIONS?
STEPS
EXAMPLE:
STEP 1
STEP 2
STEP 3
LET’S TRY SOME
ELEMENT
H2(g)
+
→
REACTANTS SIDE
KClO3 
ELEMENT
O2(g)
KCl +
REACTANTS SIDE
H2O(g)
PRODUCTS SIDE
O2
PRODUCTS SIDE
INDEPENDENT PRACTICE
Directions:
1. Check if the equation is balanced or unbalanced
2. Fill in the balancing table.
3. Fill in numbers in the table until all is equal on both sides for each element
4. Indicate type of a reaction: synthesis, decomposition, single replacement or double replacement
1.
Element
2.
Element
3.
Element
4.
Element
5.
Element
7.
Element
Type rxn:
____ Mg + ____O2  ____MgO
Reactants
Products
Type rxn:
____ Sn + ____ Cl2  ____ SnCl4
Reactants
Products
____ P + ____ O2  ____ P4O6
Reactants
Type rxn:
Products
Type rxn:
___ H2O  ____ H2 + ____O2
Reactants
Products
____ Sb + ____ Cl2  ____SbCl3
Reactants
Type rxn:
Products
____ KBr + ____ Cl2  ____ KCl + ____ Br2
Reactants
Products
Type rxn:
8.
____ Fe + ____ HCl  ____ FeCl2 + ____ H2
Element
Reactants
Type rxn:
Products
TRY THE FOLLOWING (IN YOUR OWN STYLE…)
1. Check if the equation is balanced (DO NOT BE INTIMIDATED!)
2. Start balancing with the element that has the greatest subscript (the most complicated) Balance it!
3. Treat the polyatomic ions as one thing (circle them before you begin to balance them out)
4. Balance all other element
1.
__NaCl + __BeF2 --> __NaF + __BeCl2
2.
__FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4
3.
__ SnO2 + __ C  __ Sn + __ CO
4.
__AgNO3 + __LiOH --> __AgOH + __LiNO3
5.
__Mg + __Mn2O3 --> __MgO + __Mn
If time permits…
6.
__ ZnCl2 + __ KOH  __ Zn(OH)2 + __ KCl
7.
__ Fe3O4 + __ H2  __ Fe + __ H2O
8.
__ Na2CO3 + __ HCl  __ NaCl + __ H2CO3
9.
__ Al + __ H2SO4  __ Al2(SO4)3 + __ H2
10.
__AgNO3+__(NH4)2CrO4__Ag2CrO4+ __NH4NO3
REGENTS PRACTICE
1. When the equation
Al(s) +
O2(g)
→
smallest whole numbers, the sum of the coefficients will be
(1) 9
(2) 7
(3) 3
Al2O3(s)
is correctly balanced using
(4) 12
2. Consider the following unbalanced equation.
Ag
+
H2S →
Ag2S +
H2
What is the sum of the coefficients when the equation is completely balanced using the smallest wholenumber coefficients?
(1) 5
(2) 8
(3) 10
(4) 4