1. Warm Up 01/19/2017
In your journal, write about the importance of nomenclature.
You have about 5 minutes to complete this and I will come around to check it.

2. Unit 5 - Introduction to Chemical Reactions
Module 2: Conservation of Mass in Chemical Reactions and Balancing Chemical Equations

3. Law of the Conservation of Mass
Mass cannot be created or destroyed in chemical reactions
Matter can be and is changed by the rearrangement of atoms, but the mass cannot change
Therefore, the same atoms of matter still exist after a chemical reaction as were present before the reaction

4. Balancing a Chemical Reaction
Equations describe chemical reactions showing the reactants and products
Since mass must be conserved, the same number of atoms of each element must be present in the products as were in the reactants
Individual atoms do not react alone – many atoms react at the same time
Atoms are counted using moles
The number of moles of each reactant and product must be adjusted to have the same number of atoms on both sides of the reaction
That process is known as balancing the reaction

5. How Are Reactions Balanced?
It is a process of counting atoms
The chemical formula of the compounds or elements cannot be changed – you may not change anything about the reactants or the products themselves
Only the coefficients (the number of moles) can be changed
Changing the number of moles (coefficients), changes the number of atoms of every element in the compound
Coefficients (moles) are changed until the same number of each atom are on both sides of the reaction

6. Balancing Process List the elements involved in the reaction
Count the number of moles of each element on both sides of the reaction
Adjust the number of moles using coefficients so that the first element is balanced
Recount the number of moles of each element
Repeat the process until the same number of moles is present for every element in the reaction
Check the result to make sure that the balanced reaction is the lowest whole number ratio of the reactants and products

7. Steps to Balancing a Chemical Equation
Step 1: Write a chemical formula for the reactions using formulas and symbols
Hydrogen and Oxygen combine to make water
H2 (g) + O2 (g) H2O (l)
Step 2: Count the atoms in reactants and products
Numbers and Kinds of Atoms
H2 (g) O2 (g) H2O (l) H 2 O 1

8. Steps to Balancing a Chemical Equation
Step 3: Choose coefficients that balance the equation
Remember, never change subscripts of a correct formula to balance an equation
H2 (g) + O2 (g) H2O (l)
2H2 (g) + O2 (g) 2H2O (l)
Step 4: Check the result to make sure that the balanced reaction is the lowest whole number ratio of the reactants and products

9. Steps to Writing and Balancing a Chemical Equation
Step 1: Identify the type of reaction
Reaction: magnesium bromide and sodium fluoride produce magnesium fluoride and sodium bromide
This is a double replacement reaction
Step 2: Identify whether reactants and products are ionic or covalent compounds
All are ionic compounds
Step 3: Write elements with oxidation numbers
Magnesium bromide: Mg+2 and Br‐1
Sodium fluoride: Na+1 and F‐1
Magnesium fluoride: Mg+2 and F‐1
Sodium bromide: Na+1 and Br‐1

10. Steps to Writing and Balancing a Chemical Equation
Step 4: Write compounds. Be sure charges balance out to zero!
Because Mg+2 has an overall positive charge of +2, you must have a negative charge of ‐2 to balance out to zero. You need 2 atoms of Br‐1
This compound becomes MgBr2
Na+1 and F‐1 becomes NaF
Mg+2 and F‐1 becomes MgF2
Na+1 and Br‐1 becomes NaBr
Step 5: Write out the equation
MgBr2 + NaF è MgF2 + NaBr
Step 6: Balance the equation
MgBr2 + 2NaF è MgF2 + 2NaBr