Balancing Chemical Equations Basics

Subscript

• written in front of a chemical formula (2NaCl) or symbol (2Li)

• tells you how many molecules of that substance there are

Coefficient

Coefficient VS Subscript

Some text here about the topic of discussion

• written after a chemical symbol (Cl₂)

• tells you how many atoms of that substance (element) there are

Multiple Choice

How many atoms of Mg are in the following compound: MgF₂

• 0

• 1

• 2

• 3

Multiple Choice

How many atoms of F are in the following compound: MgF₂

• 0

• 1

• 2

• 3

Multiple Choice

How many atoms of Cl are in the following compound: 2NaCl

• 0

• 1

• 2

• 3

Multiple Choice

How many atoms of O are in the following compound: 2Na₂O

• 1

• 2

• 3

• 4

Multiple Choice

How many atoms of Na are in the following compound: 2Na₂O

• 1

• 2

• 3

• 4

Multiple Choice

To balance a chemical equation, we change the _________ .

• coefficients

• subscripts

• types of atoms

• types of compounds

Poll

Are you READY to practice balancing equations?

• Yes, of course!

• Maybe

• I think so

Multiple Choice

When counting atoms in an equation, you ______ the coefficient and subscript.

• add

• subtract

• multiple

• divide

Balancing Chemical Equations

1. Write out the equation on lined paper, and divide it into a chart with one side for the reactants and one side for the products.

2. List the elements on the reactants and the products sides of the chart.

3. Count the atoms on the reactants and the products sides of the equation.

4. Find any unbalanced atoms.

5. Use coefficients to balance the atoms.

   • Only put coefficients before a chemical formula, not in the middle.

   • Only change coefficients, not the formulas of the compounds.

   • Repeat steps 4 and 5 as needed until all atoms are balanced.

6. Check that all atoms are balanced.

​Na + MgF₂    ➔   NaF +   Mg

​Na =

Mg =

F =

​Na =

Mg =

F =

​#1

​Na + MgF₂    ➔   NaF +   Mg

​Na = 1

Mg = 1

F = 2

​Na = 1

Mg = 1

F = 1

Multiple Choice

Is the equation (Na + MgF₂ ➔ NaF + Mg) balanced?

• Yes

• No

​Na + MgF₂    ➔   2NaF +   Mg

​Na = 1

Mg = 1

F = 2

​Na = 1 x 2 = 2

Mg = 1

F = 1 x 2 = 2

​2Na + MgF₂    ➔   2NaF +   Mg

​Na = 1 x 2 = 2

Mg = 1

F = 2

​Na = 1 x 2 = 2

Mg = 1

F = 1 x 2 = 2

Multiple Choice

Is the equation (2Na + MgF₂ ➔ 2NaF + Mg) balanced?

• Yes

• No

​ Mg + HCl    ➔  MgCl₂  +    H₂

​Mg =

H =

Cl =

​Mg =

H =

Cl =

​#2

​ Mg + HCl    ➔  MgCl₂  +    H₂

​Mg = 1

H = 1

Cl = 1

​Mg = 1

H = 2

Cl = 2

​ Mg + 2HCl    ➔  MgCl₂  +    H₂

​Mg = 1

H = 1 x 2 = 2

Cl = 1 x 2 = 2

​Mg = 1

H = 2

Cl = 2

​Cl₂  +     KI    ➔       KCl   +     I₂

​Cl =

K =

I =

​Cl =

K =

I =

​#3

​Cl₂  +     KI    ➔       KCl   +     I₂

​Cl = 2

K = 1

I = 1

​Cl = 1

K = 1

I =2

​Cl₂  +     KI    ➔      2KCl   +     I₂

​Cl = 2

K = 1

I = 1

​Cl = 1 x 2 = 2

K = 1 x 2 = 2

I =2

​Cl₂  +    2KI    ➔     2KCl   +     I₂

​Cl = 2

K = 1 x 2 = 2

I = 1 x 2 = 2

​Cl = 1 x 2 = 2

K = 1 x 2 = 2

I =2

​NaCl   ➔      Na +      Cl₂ 

​Na =

Cl =

​Na =

Cl =

​#4

​NaCl   ➔      Na +      Cl₂ 

​Na = 1

Cl = 1

​Na = 1

Cl = 2

​2NaCl   ➔      Na +      Cl₂ 

​Na = 1 x 2 = 2

Cl = 1 x 2 = 2

​Na = 1

Cl = 2

​2NaCl   ➔     2Na +      Cl₂ 

​Na = 1 x 2 = 2

Cl = 1 x 2 = 2

​Na = 1 x 2 = 2

Cl = 2

​Na + O₂    ➔       Na₂O

​Na = 1

O = 2

​Na = 2

O = 1

​#5

​Na + O₂    ➔      2Na₂O

​Na = 1

O = 2

​Na = 2 x 2 = 4

O = 1 x 2 = 2

​4Na + O₂    ➔      2Na₂O

​Na = 1 x 4 = 4

O = 2

​Na = 2 x 2 = 4

O = 1 x 2 = 2

​Na + HCl    ➔    H₂   +    NaCl 

​Na =

H =

Cl =

​Na =

H =

Cl =

​#6

​Na + HCl    ➔    H₂   +    NaCl 

​Na = 1

H = 1

Cl = 1

​Na = 1

H = 2

Cl = 1

​Na + 2HCl    ➔    H₂   +    NaCl 

​Na = 1

H = 1 x 2= 2

Cl = 1 x 2= 2

​Na = 1

H = 2

Cl = 1

​Na + 2HCl    ➔    H₂   +   2NaCl 

​Na = 1

H = 1 x 2= 2

Cl = 1 x 2= 2

​Na = 1 x 2 = 2

H = 2

Cl = 1 x 2 = 2

​2Na + 2HCl    ➔    H₂   +   2NaCl 

​Na = 1 x 2= 2

H = 1 x 2= 2

Cl = 1 x 2= 2

​Na = 1 x 2 = 2

H = 2

Cl = 1 x 2 = 2

K + Cl₂    ➔          KCl 

K = 1

Cl = 2

​K = 1

Cl = 1

​#7

K + Cl₂    ➔         2KCl 

K = 1

Cl = 2

​K = 1 x 2 = 2

Cl = 1 x 2 = 2

2K + Cl₂    ➔         2KCl 

K = 1 x 2 = 2

Cl = 2

​K = 1 x 2 = 2

Cl = 1 x 2 = 2

Multiple Choice

How many atoms of C are there in the reactant side of the equation:

CaCO₃ → CaO + 2CO₂

• 1

• 2

• 3

Multiple Choice

How many atoms of C are there in the product side of the equation:

CaCO₃ → CaO + 2CO₂

• 1

• 2

• 3

Multiple Choice

How many atoms of O are there in the reactant side of the equation:

CaCO₃ → CaO + 2CO₂

• 2

• 3

• 4

• 5

Multiple Choice

How many atoms of O are there in the reactant side of the equation:

CaCO₃ → CaO + 2CO₂

• 2

• 3

• 4

• 5

Multiple Choice

Decide of the following equation is balanced or unbalanced: CaCO₃ → CaO + 2CO₂

• balanced

• unbalanced

CaCO₃ → CaO + 2CO₂

Ca = 1

C = 1

O = 3

Ca = 1

C = 2

O = 1 + (2 x 2) = 5

UNBALANCED

Poll

How well do you understand balancing equations?

• Very well

• I need more practice

• I am confused