Name:______Date:______

3.3 How do we balance equations? 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

H2(g) + O2(g) → H2O(g)

ELEMENT / REACTANTS SIDE / PRODUCTS SIDE

KClO3 à KCl + O2

ELEMENT / REACTANTS SIDE / 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. ____ Mg + ____O2 à ____MgO

Element / Reactants / Products

2. ____ Sn + ____ Cl2 à ____ SnCl4

Element / Reactants / Products

3. ____ P + ____ O2 à ____ P4O6

Element / Reactants / Products

4. ___ H2O à ____ H2 + ____O2

Element / Reactants / Products

5. ____ Sb + ____ Cl2 à ____SbCl3

Element / Reactants / Products

7. ____ KBr + ____ Cl2 à ____ KCl + ____ Br2

Element / Reactants / Products

8. ____ Fe + ____ HCl à ____ FeCl2 + ____ H2

Element / Reactants / 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 à __ Sn + __ CO

4. __AgNO3 + __LiOH --> __AgOH + __LiNO3

5. __Mg + __Mn2O3 --> __MgO + __Mn

If time permits…

6. __ ZnCl2 + __ KOH à __ Zn(OH)2 + __ KCl

7. __ Fe3O4 + __ H2 à __ Fe + __ H2O

8. __ Na2CO3 + __ HCl à __ NaCl + __ H2CO3

9. __ Al + __ H2SO4 à __ Al2(SO4)3 + __ H2

10. __AgNO3+__(NH4)2CrO4à__Ag2CrO4+ __NH4NO3

REGENTS PRACTICE

1. When the equation Al(s) + O2(g) → Al2O3(s) is correctly balanced using smallest whole numbers, the sum of the coefficients will be

(1) 9 (2) 7 (3) 3 (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 whole-number coefficients?

(1) 5 (2) 8 (3) 10 (4) 4