Chemical Reactions and Quantities (Ch. 6)

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Chemical Reactions and Quantities (Ch. 6)

• Chemical Change vs. Physical Change
• In a chemical reaction, reacting substances take
  on new formulas and properties.
• In a physical change only appearance, not
  composition,
• is altered.
• Chemical Equations
• Reactants Products

? Heat (s) Solid (g) gas (l) Liquid (aq)
Dissolved in H2O
2

• In a chemical reaction, bonds are both broken
  and
• Formed.
• Atoms are not gained, lost, or changed into
  other atoms
• Therefore, we must write a chemical reaction as a
  
• Balanced equation
• Balance the following chemical equations

2H2 (g) O2(g)
2H2O(l)
N2 (g) O2 (g)
NO (g) Fe (s) O2 (g)
Fe2O3 (s) Pb(NO3)2 (s) NaCl (s)
PbCl2 (s) 2Na(NO3) (s)
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Types of Chemical Reactions

• Combination A B C
• Decomposition AB A B
• Single Replacement AB C
  A BC
• Double Replacement AB CD AD
  CB
• Combustion Reactants O2
  CO2 H2O

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Oxidation-Reduction Reactions

• Loss and gain of electrons among reactants

Ca S CaS Ca
Ca2 2e- (oxidation) S 2e-
S2- (reduction) Practice Zn CuSO4
ZnSO4 Cu
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Mole Relationships in Chemical Equations
2Ag S Ag2S 2
mol Ag needed for every 1 mole S reacted
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2 mol Ag 1 mol S 1 mol
Ag2S
2 atoms Ag 1 atom S 1
molecule Ag2S
2 (6.02 x 1023 atoms Ag) 1 (6.02 x 1023 atoms
S) 1 (6.02 x 1023 molecules Ag2S)
2 (107.9 g Ag) 1 (32 g S)
1 (247.9 g Ag2S) 247.9 g reactant
247.9 g product
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Mole to Mole Relationships in a Chemical Equation
2Fe 3S Fe2S3
We can write the following equalities 2
mol Fe 3 mol S 3 mol S 2 mol Fe
How many mol of S are needed to react with 6.0
mol of Fe?
6.0 mol Fe (
)
3 mol S 2 mol Fe

9 mol S
8
C3H8 5O2 3CO2
4H2O
How many mol of CO2 are produced when 6 mol C3H8
react?
N2 O2 2NO
How many grams of NO are produced when 1.5 mol
of O2 react?