Chp.12/Activity #4 Chemical Equations (p792)

Due Today:

HW. Number of atoms in a formula

Learning targets•Represent chemical changes using word equations

and chemical equations.•Use the principle of conservation of matter to

balance chemical reactions.

2/25/2015Wednesday

1. Carbon Monoxide2. CCl4

3. Iron (III) Oxide4. Al2(SO4)3

5. CuF2

6. Magnesium Sulfate

7. How does an ionic compound form? What forms the bond?8. How does a covalent compound form? What forms the

bond?

COCarbon TetrachlorideFe2O3

Aluminum SulfateCopper (II) FlourideMgSO4

Chemical Reactions and Equations

• The scientific word for chemical change is “Chemical Reaction”• Chemical Reactions are written in Chemical Equations.• E.g. Zn + 2HCl -> ZnCl2 + H2 is a chemical equation.

• A Chemical Reaction involves the breaking/formation of chemical bonds• E.g. H-Cl bond is broken and H-H bond is newly formed.

Law of Conservation of Mass

•Matter is never created or destroyed.• So the Total Mass of the Reactants and the Products need to be the same.

• E.g. Zn + 2HCl -> ZnCl2 + H2

Element Reactants Products

Zn 1 1

Cl 2 2

H 2 2

Both sides have the same number and kind of elements!

Balancing Chemical Equations

• You first need to be able to count the number of atoms.• Coefficients (always whole numbers) tell us how many

compounds we have.• E.g. 2HCl means we have 2 of the HCl molecules.

(total of 2 Hydrogen and 2 Chlorine atoms)• E.g. 6ZnCl2 means we have 6 of the ZnCl2 molecules.

(total of 6 Zinc and 12 Chlorine atoms)• Tip: Multiply the Coefficient with subscripts to get the

number of atoms.

Balancing Chemical Equations

• Reactants and Products need to have the same number of atoms for the same elements.• Elements are not created or destroyed in a chemical reaction.

• Use the Element Inventory to keep track of atoms.• Change coefficients to match the number of atoms.

E.g. NaOH + H2SO4 -> Na2SO4 + H2O

Element Reactants ProductsNa 1 2S 1 1O 5 5H 3 2

Important: Change One Coefficient at a time.

E.g. 2NaOH + H2SO4 -> Na2SO4 + H2O

Element Reactants ProductsNa 2 2S 1 1O 6 5H 4 2

E.g. 2NaOH + H2SO4 -> Na2SO4 + 2H2O

Element Reactants ProductsNa 2 2S 1 1O 6 6H 4 4

Done!

Can you balance these chemical equations?1. NaCl + BeF2 -> NaF + BeCl2 2NaCl + BeF2 -> 2NaF + BeCl2

2. FeCl3 + Be3(PO4)2 -> BeCl2 + FePO4

2FeCl3 + Be3(PO4)2 -> 3BeCl2 + 2FePO4

3. CH4 + O2 -> CO2 + H2O

CH4 + O2 -> CO2 + 2H2O

4. AgNO3 + LiOH -> AgOH + LiNO3

AgNO3 + LiOH -> AgOH + LiNO3

A Beginner’s Guide to Balancing Equations• https://www.youtube.com/watch?v=_B735turDoM