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. 2/25/2015 Wednesday

1.Carbon Monoxide 2.CCl 4 3.Iron (III) Oxide 4.Al 2 (SO 4 ) 3 5.CuF 2 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? CO Carbon Tetrachloride Fe 2 O 3 Aluminum Sulfate Copper (II) Flouride MgSO 4

Chemical Reactions and Equations The scientific word for chemical change is “Chemical Reaction” Chemical Reactions are written in Chemical Equations. E.g. Zn + 2HCl -> ZnCl 2 + H 2 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 -> ZnCl 2 + H 2 ElementReactantsProducts Zn11 Cl22 H22 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. 6ZnCl 2 means we have 6 of the ZnCl 2 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 + H 2 SO 4 -> Na 2 SO 4 + H 2 O ElementReactantsProducts Na12 S11 O55 H32 Important: Change One Coefficient at a time.

E.g. 2NaOH + H 2 SO 4 -> Na 2 SO 4 + H 2 O ElementReactantsProducts Na22 S11 O65 H42

E.g. 2NaOH + H 2 SO 4 -> Na 2 SO 4 + 2H 2 O ElementReactantsProducts Na22 S11 O66 H44 Done!

Can you balance these chemical equations? 1. NaCl + BeF 2 -> NaF + BeCl 2 2NaCl + BeF 2 -> 2NaF + BeCl 2 2. FeCl 3 + Be 3 (PO 4 ) 2 -> BeCl 2 + FePO 4 2FeCl 3 + Be 3 (PO 4 ) 2 -> 3BeCl 2 + 2FePO 4 3. CH 4 + O 2 -> CO 2 + H 2 O CH 4 + O 2 -> CO 2 + 2H 2 O 4. AgNO 3 + LiOH -> AgOH + LiNO 3 AgNO 3 + LiOH -> AgOH + LiNO 3

A Beginner’s Guide to Balancing Equations