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6.5 Balancing Chemical Equations A skeleton equation represents all chemicals by their symbols and by numbers. It is NOT balanced. Skeleton equations and chemical equations are universal. They can be understood in every language all over the world! Word Equation methane + oxygen ➡ water + carbon dioxide CH4 + O2 ➡ H2O Skeleton Equation + CO2 In a balanced chemical equation the reactants and the products contain equal numbers of atoms of each type. (If the reactants have 4 O then the products will have 4 O atoms) This follows the Law of Conservation of Mass. Use these steps to balance an equation. 1. Determine the correct formulas and write the skeleton equation: Fe 2. ➜ O2 Fe3O4 Count the number of atoms of each element in the reactants and products. (Polyatomic ions appearing unchanged on each side are counted as a single unit). (A table is easiest) Type of Atom Reactants Products Fe 1 3 O 2 4 3. Balance the elements one at a time by using coefficients. The coefficient is a whole number that appear in front of the formula in an equation. When no coefficient is written, it is assumed to be 1. 3 Fe 4. 5. + + ➜ 2 O2 Fe3O4 Always check to be sure that the equation is balanced. Type of Atom Reactants Products Fe 3 3 O 4 4 Make sure all coefficients are in the lowest possible ratio. (Reduce if possible) Hints: Never add extra compounds Never change formulas (subscripts) If an element appears in only one compound on each side balance this one first. When one of the products or reactants is a free element (only one type of atom) balance this last. 1 TRY THESE: 1. _____C2H6 + _____O2 ---> _____H2O + _____CO2 2. _____O2 + _____C6H12O6 ---> _____H2O + _____CO2 3. ___Br2 + ___H2O + ___SO2 ---> ___HBr + ___H2SO4 4. _____KOH + _____H3PO4 ---> _____K3PO4 + _____H2O 5. ______Zn + ______HCl ---> ______ZnCl2 + ______H2 6. ______KClO3 ---> ______KCl + ______O2 7. ______S8 + ______F2 ---> ______SF6 8. ______Fe + ______O2 ---> ______Fe2O3 2