Balancing Chemical Equations

Warm Up

1. What is a chemical reaction?

1. What are the reactants? What are the products?

EQ: How do we balance chemical equations?HOT Q1: What is a chemical reaction?HOT Q2: What does the law of conservation of mass state?HOT Q3: What are the steps for balancing chemical equations?

Agenda

• Warm Up/Objective • How ‘Bout Them Apples• Chemical Reaction Notes • Chemical Reaction Practice • Worksheet 7.2 • Exit Ticket

Chemical Reaction Notes

1. Chemical Reaction - a process that leads to the transformation

of one set of chemical substances to another

Notes

Chemical Reaction Notes

2. Two Sides of the Chemical Equation

-Reactants – -Products –

___Li + ___Br2 ___ LiBr

Notes

Reactants Products

What’s up with the apples?

How ‘Bout Them Apples

Chemical Reactions

LiBr Br

Li LiBrBr

Li

• For the rest of today, we will be balancing chemical equations.

• This will seem like a bunch of rules a chemist made up unless you understand the following concepts.

Chemical Reaction Notes1. Law of Conservation of Mass

2. Chemical reactions MUST BE BALANCED-The number of atoms on the reactant side and the product side must be EQUAL

Notes

But how do we count the number of atoms?

Counting Atoms Rules

1. Subscripts apply to the element immediately before it

Ex) MgCl2 #Mg ____ #Cl_____

2. Coefficients multiply the entire moleculeEx) 2C6H2 #C___ #H____

3P6Cl3

3. If there are parentheses, the subscript multiples everything inside the parenthesesEx) 3Be(NO3)2 #Be___ #N____ #O____

Counting Atoms• How many atoms of each element are in the How many atoms of each element are in the

following molecules?following molecules?

1. H1. H22SOSO44

2. Ca(OH)2. Ca(OH)22

3. NaCl3. NaCl4. (NH4. (NH33))33POPO44

5. 3H5. 3H22OO

• To decide if an equation is balanced, compare the number of atoms of each element that appear on each side of the equation. If the number of atoms is equal then the equation is balanced, if not equal than the equation is not balanced

Ex) N2 + 3 H2 2 NH3

Is it balanced?

You Try!

C3H8 + 5 O2 3 CO2 + 4 H2O

Is is balanced?

Ok, cool.

• BUT HOW DO WE BALANCE THESE BAD BOYS????!!!

When balancing…

Step 1: Draw a line between products and reactants

Step 2: Tally up atoms of each element on each side

Step 3: Change coefficients to start balancing(never change subscripts!)

Step 4: Recalibrate each time you change a coefficient

Step 5: CHECK YOUR WORK!

Balancing Chemical Reactions

Ex 1: ____N2 + ____H2 ___NH3

Notes

Balancing Chemical Reactions

Ex 2: ____FeO ____Fe + ____O2

Notes

• The best way to learn this is to practice.

• With a partner, balance the following equations:

1.____NO + ____O2 ___NO2

2.____H2 + ____Cl2 ___HCl

3.____Fe + ____Cl2 ___FeCl3

4. ____CH4 + ____O2 ___CO2 + ___H2O

Partner Practice

1. ____NO + ____O2 ___NO2

Partner Practice

2. ____H2 + ____Cl2 ___HCl

Partner Practice

3. ____Fe + ____Cl2 ___FeCl3

Partner Practice

4. ____CH4 + ____O2 ___CO2 + ___H2O

Partner Practice

5. ____ K + ____ Cl2 ____ KCl

6. ____ N2 + ____ F2 ____ NF3

Independent Practice

For the rest of class, work on (and complete, if possible) Worksheet 6.1

If you get done: come and see me. If you are done, I will have you check your answers against my answer key. If you get any wrong, you must go back and fix them.

If you get done with that: You may help a neighbor for beast mode status.

Exit Ticket

Balance the following equations:

1.___Na + ___Cl2 ___NaCl

2.___Al + ___HBr ___AlBr3 + ___H2

• ___GaF3 + ___ Cs ___ CsF + ___ Ga

• ___ CF4 + ___Br2 ___CBr4 + ___F2

• ___SeCl6 + ___O2 ___SeO2 + ___Cl2