1. Chemical Equations

2. A Chemical Reaction Reactants Products Yields (produces)

3. Writing a Chemical Equation Chemical symbols give a “before-and-after” picture of a chemical reaction ReactantsProducts MgO + CCO + Mg magnesium oxide to yield carbon monoxide reacts with carbon and magnesium

4. Ways to represent a chemical reaction: 1.Word Equation hydrogen + oxygen  water 2.Skeleton Equation H 2 + O 2  H 2 O 3.Balanced Equation 2H 2 + O 2  2H 2 O

5. Balancing Equations 1.Write the skeleton equation Make sure compound adds to zero using subscripts Mg + O 2  MgO 2. Start counting on the left and balance using coefficients ___ Mg + ___ O 2  ___ MgO 3. At arrow repeat until done You can make odd numbers even ( X 2) +2 -2 2

6. Steps in Balancing An Equation Fe 3 O 4 + H 2 Fe + H 2 O Fe: Fe 3 O 4 + H 2 3 Fe + H 2 O O:Fe 3 O 4 + H 2 3 Fe + 4 H 2 O H: Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O

7. What does it mean? 4 Al(s) + 3 O 2 (g) ---> 2 Al 2 O 3 (s) This equation means 4 Al atoms + 3 O 2 molecules - --produces---> 2 molecules of Al 2 O 3 2 molecules of Al 2 O 3 AND/OR AND/OR 4 moles of Al + 3 moles of O 2 - --produces---> 2 moles of Al 2 O 3 2 moles of Al 2 O 3

8. Balancing Equations ___ Al(s) + ___ Br 2 (l) ---> ___ Al 2 Br 6 (s) 23

9. Learning Check: Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O A. Number of H atoms in 4 H 2 O 1) 22) 43) 8 B. Number of O atoms in 4 H 2 O 1) 22) 43) 8 C. Number of Fe atoms in Fe 3 O 4 1) 12) 33) 4

10. Practice 1.__N 2 + __H 2  __NH 3 2.__NH 3 + __O 2  __HNO 3 + __H 2 O 3.__H 2 + __Fe 2 O 3  __Fe + __H 2 O 4.__C 2 H 4 + __O 2  __CO 2 + __H 2 O 3 2 2 3 2 3 3 2 2

11. Harder Practice! 1.__Na + __H 2 O  __NaOH + __H 2 2.__NH 3 + __O 2  __NO + __H 2 O 3.Copper (II) sulfide + nitric acid  copper (II) sulfate + nitrogen dioxide + water __CuS + __HNO 3  __CuSO 4 + __NO 2 + __H 2 O 2 2 2 4 5 4 6 8 8 4