Balancing Equations- Intro and Notes

Think about it Baking a cake Cake mix 3 eggs 1/3 cup of vegetable oil When you bake it, do you gain or lose ingredients??

Agenda Drill Balancing Equations with Pipecleaners and Beads Notes and Practice Exit Slip

Looking at a chemical equation…

Before Moving On… How many aluminums are in Al(NO3)3? How many nitrogens are in Al(NO3)3? How many oxygens are in Al(NO3)3?

Instructions You will work on 5 different equations with a partner To balance equations, you need the same number of each type of atom on the reactants side and products side Use the beads and coding sheet (explaining which color represents each bead) to diagram each reaction

Keep track of the number of atoms on each side of the reaction Manipulate the reactants and products until you reach the same number of atoms on each side. Add numbers to the blanks that match your work!

Example _____H2 + _____O2  _____H2O Reactants Products H O  

Before moving on… 12 Blue Beads 16 Pink Beads 6 Red Beads 12 Green Beads 4 Orange Beads 4 Yellow Beads 4 Purple Beads 14 Pipecleaners

What is YOUR Definition of the Law of Conservation of Mass???

Law of Conservation of Mass Mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. AKA: The mass of the products in a chemical reaction must equal the mass of the reactants.

https://www.youtube.com/watch?v=J5hM1DxaPLw

How is balancing an equation like baking a cake? Question How is balancing an equation like baking a cake?

Soo… Why Balance Equations??? Law of Conservation of Mass!!! In order for the mass to remain the same, the number of atoms of each element must be the same before and after a chemical reaction

Try Balancing On Your Own In your groups… Balance the equations given On the whiteboard, write the steps (in words) of how you would balance an equation

What are your Steps?

Answers N2 + 3 H2  2 NH3 S8 + 8 O2  8 SO2 2 AlBr3 + 3 Cl2  2 AlCl3 + 3 Br2 4 Cr + 3 O2  2 Cr2O3 BaCl2 + (NH4)2CO3  BaCO3 + 2 NH4Cl

Steps for Balancing Count the number of atoms of each type appearing on both sides Balance the elements one at a time by adding coefficients Check to make sure it is balanced

Add a subscript to make an equation balanced? Can I…??? Add a subscript to make an equation balanced? Think about… H2 + O2  H2O

NEVER!!!!! Change a subscript to balance an equation If you change the formula you are describing a different reaction H2O is a different compound than H2O2 Never put a coefficient in the middle of a formula 2 NaCl is okay, Na2Cl is not Never have a fraction as a coefficient ½ H2 is not okay

Helpful Hints First balance elements that occur in the fewest formulas; oxygen and hydrogen are usually balanced last Coefficients must be whole numbers and reduced to the lowest ration If you get 4-2-2, divide all numbers by 2 to get 2-1-1 Polyatomic ions often remain intact during a chemical reaction, so they can be treated as single entities

Helpful Hints Continued Sometimes you will insert a coefficient but later determine it is wrong, so you will have to take it out and reinsert a new coefficient If it appears there is no possible solution using whole number coefficients, multiply the entire equation by 2

What’s Next Exit Slip Continue to practice balancing equations

Practice __ H2 + ___ O2  ___ H2O __ SO2 + ___ O2  ___ SO3

Answers N2 + 3 H2  2 NH3 2 SO2 + O2  2 SO3