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
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