Topic: Stoichiometry: Balancing Chemical Equations Do Now:

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Topic Stoichiometry Balancing Chemical
EquationsDo Now
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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

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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

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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)
• - lets figure out how to balance

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Equation Balancinglets RAPR A
PSnO2(s) H2(g) ? Sn(s) H2O(g)
Sn O H
- 1
1 -
- 1
2 -
- 2
2 -
NOT BALANCED
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SnO2(s) H2(g) ? Sn(s) H2O(g)
2
2
Sn O H
- 1
1 -
- 1
2 -
2
- 2
2 -
4
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• 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 ?
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NOTE Coefficients must be in lowest possible
ratios 2SnO2(s) 4H2(g) ? 2Sn(s)
4H2O(g)
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Fe O2 ? Fe2O3

• HINTS
• Most Complex Fe2O3
• ODDS ARE AKWARD, so Try to make O3 even!!!!!!!

4Fe 3O2 ? 2 Fe2O3
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AgNO3 MgCl2 ? Mg(NO3)2 AgCl

• HINTS
• Keep polyatomics together
• NO3
• Ag
• Cl
• Mg

2 AgNO3 MgCl2 ? Mg(NO3)2 2 AgCl
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Na H2O ? NaOH H2

• HINTS
• ODDS ARE AKWARD try to make even
• H on product side H H2 3 hydrogens

• 2 Na 2 H2O ? 2 NaOH H2