2. 7.4 BALANCIN G CHEMICAL EQUATION S Patrick Mattoon Keller Bean Griffin Rice

3. THE LAW OF CONSERVATION OF MASS  Chemical reactions are rearranged, never added or destroyed  Each side of the equation must have an equal number of atoms for each element  The mass of the reactants must equal the mass of the products

4. BALANCING EQUATIONS  Balanced Equation: each side of the equation has the same number of atoms of each element  In the equation if you label the state of matter, the symbol (g,s,l,or aq) is put directly following the formula Ex.) SnO 2 (s)  Balance the metals before nonmetals

5. RULES FOR BALANCING EQUATIONS 1. Write the equation (leave spaces in front of the formulas for coefficients) 2. Add the subscripts of each separate atom on either side of the equation 3. Balance chemical formulas by placing coefficients in front of them. Do not add or change subscripts, that will change the formulas 4. Make sure all of the coefficients are in the lowest possible ratio 5. Check to make sure the number of each atom is equal on either side of the equation http://chemistry.about.com/cs/stoichiometry/a/aa042903a.htm

9. D. Fe 2 O 3 +2C 2Fe+4CO 2 B. 2Fe 2 O 3 +3C 4Fe+3CO 2 Fe 2 O 3 +C Fe+CO 2 A. 6Fe 2 O 3 +6C 3Fe+2CO 2 C. 3Fe 2 O 3 +4C 6Fe+3CO 2

10. COMBUSTION C H O Always balance the carbon and hydrogen atoms before the oxygen atoms

16. HOMEWORK PROBLEMS a) 2KClO 3 KCl+O 2 b) 2Na+Cl 2 NaCl c) P 4 O 10 +H 2 O H 3 PO 4

17. THE END