1. Starter  Write the word equation from the following description: Zinc metal is added to hydrochloric acid to create zinc chloride and hydrogen gas.

2. Ch. 8 Chemical Equations and Reactions 8.1b Balancing Equations and Writing Formula Equations

3. Balancing Equations  ONLY add/change coefficients- NEVER subscripts!!! 1. balance one type of atom at a time 2. balance polyatomic ions first 3. balance atoms that appear only once second 4. balance H and O last 5. simplify if you can 6. Check at end!

4. Writing Equations  Write Word equations to help you organize reactants and products  Be sure to include symbols showing states of each reactant and product  Be sure to write the correct formula for each (crossing over for ionic compounds!)  Check your balancing of the equation when you are finished

5. Example 1  Description: Zinc metal is added to hydrochloric acid to create zinc chloride and hydrogen gas.  Word Equation: zinc + hydrochloric acid  zinc chloride + hydrogen

6. Example 1  Formula Equation: Zn (s) + HCl(aq)  ZnCl 2 (aq) + H 2 (g)  Balanced Formula Equation Zn (s) + 2HCl(aq)  ZnCl 2 (aq) + H 2 (g)

7. Example 2  Solid calcium metal reacts with water to form aqueous calcium hydroxide and hydrogen gas.  calcium + water  calcium hydroxide + hydrogen  Ca(s) + H 2 O(l)  Ca(OH) 2 (aq) + H 2 (g)  Ca(s) + 2H 2 O(l)  Ca(OH) 2 (aq) + H 2 (g)

8. Example 3  solid zinc metal reacts with aqueous copper (II) sulfate to produce solid copper metal and aqueous zinc sulfate  zinc + copper (II) sulfate  copper + zinc sulfate  Zn(s) + CuSO 4 (aq)  Cu(s) + ZnSO 4 (aq)

9. Example 4  Hydrogen peroxide in an aqueous solution decomposes to produce oxygen and water  hydrogen peroxide  oxygen + water  H 2 O 2 (aq)  O 2 (g) + H 2 O(l)  2H 2 O 2 (aq)  O 2 (g) + 2H 2 O(l)

10. Example 5  Solid copper metal reacts with aqueous silver nitrate to produce solid silver metal and aqueous copper (II) nitrate  copper + silver nitrate  silver + copper (II) nitrate  Cu(s) + AgNO 3 (aq)  Ag(s) + Cu(NO 3 ) 2 (aq)  Cu(s) + 2AgNO 3 (aq)  2Ag(s) + Cu(NO 3 ) 2 (aq)

11. Example 6  Carbon dioxide gas is bubbled through water containing solid barium carbonate, creating aqueous barium bicarbonate  carbon dioxide + water + barium carbonate  barium bicarbonate  CO 2 (g) + H 2 O(l) + BaCO 3 (s)  Ba(HCO 3 ) 2 (aq)

12. Example 7  Acetic acid solution is added to a solution of magnesium bicarbonate to create water, carbon dioxide gas, and aqueous magnesium acetate.  acetic acid + magnesium bicarbonate  water + carbon dioxide + magnesium acetate  HCH 3 COO(aq) + Mg(HCO 3 ) 2 (aq)  H 2 O(l) + CO 2 (g) + Mg(CH 3 COO) 2 (aq)  2HCH 3 COO(aq) + Mg(HCO 3 ) 2 (aq)  2H 2 O(l) + 2CO 2 (g) + Mg(CH 3 COO) 2 (aq)