Topic: Stoichiometry: Balancing Chemical Equations Do Now:

What is stoichiometry? The study of quantitative relationships in a balanced chemical equation Balance equations represent chemical reactions Remember in chemical reactions 3 things are conserved Matter Energy charge

Law of Conservation of Matter Matter is neither created nor destroyed in a chemical reaction Mass reactants = Mass products Chemical bonds in reactants may break New bonds may form to produce products Number of atoms of each element is “constant” # of atoms of each element is the same on both sides of the equation

Writing Chemical Equations Begin with word equation Solid Tin (IV) Oxide is heated with Hydrogen gas to form tin metal and water vapor. Next go to skeleton equation: replace names of substances with chemical formulas SnO2(s) + H2(g)  Sn(s) + H2O(g) Balance skeleton equation: # of atoms of each element is the same on both sides of the equation (law of conversation of mass) - let’s figure out how to balance

Equation Balancing… let’s RAP R A P SnO2(s) + H2(g)  Sn(s) + H2O(g) 1 - - 1 2 - - 1 2 - - 2 NOT BALANCED

SnO2(s) + H2(g)  Sn(s) + H2O(g) 1 - - 1 2 - - 1 2 4 2 - - 2 4 Find the most complex compound and then compare the number of each element on product side and reactant side Look at H2O – 2 Hydrogen and 1 oxygen On reactant side, 2 Oxygen and 2 Hydrogen Use Coefficients to balance the numbers of each atom, check number of atoms as you go: NOTE: NEVER CHANGE SUBSCRIPTS BALANCED 

2SnO2(s) + 4H2(g)  2Sn(s) + 4H2O(g) NOTE: Coefficients must be in lowest possible ratios 2SnO2(s) + 4H2(g)  2Sn(s) + 4H2O(g)

Fe + O2  Fe2O3 4Fe + 3O2  2 Fe2O3 HINTS: Most Complex = Fe2O3 ODDS ARE AKWARD, so Try to make O3 even!!!!!!! 4Fe + 3O2  2 Fe2O3

AgNO3 + MgCl2  Mg(NO3)2 + AgCl HINTS: Keep polyatomics together NO3 Ag Cl Mg 2 AgNO3 + MgCl2  Mg(NO3)2 + 2 AgCl

Na + H2O  NaOH + H2 HINTS: 2 Na + 2 H2O  2 NaOH + H2 ODDS ARE AKWARD – try to make even H on product side H + H2 = 3 hydrogens 2 Na + 2 H2O  2 NaOH + H2