Section 3'6: Quantitative Information from Balanced Equations

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Section 3.6 Quantitative Information from
Balanced Equations
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3.6 Quantitative Information from Balanced
Equations.

• The coefficients in a balanced equation
  represent both the relative numbers of molecules
  involved in the reaction, AND THE RELATIVE
  NUMBERS OF MOLES, and therefore the relative
  masses
• 2 H2(g) O2(g) ? 2 H2O (l)
• 2 molecules 1molecule 2 molecules
• 2 moles 1 mole 2 moles
• 2 x (2.0) g 32.0 g ? 2 x (18.0) g

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Weights of products and reactants in a balanced
equation

• We can thus work out how many grams of water
  will be produced by burning given amounts of H2
  and O2 together.
• Example The combustion of butane
• 2 C4H10(l) 13 O2(g) ? 8 CO2(g) 10 H2O(l)
• 2 moles 13 moles 8 moles 10 moles
• 2 x 58.0 g 8 x 44.0 g

M. Wt. C4H10 M. Wt. CO2
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Conversion Sequence
Grams Reactant
Moles Reactant
Moles Product
Grams Product
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How many grams of CO2 will be obtained by burning
1.00 g of C4H10?

• 2C4H10 13O2 ? 8CO2(g) 10H2O(g)
• 1) Grams reactant ? Moles reactant
• 1.00 g x 1mol C4H10 0.0172 mol C4H10
• 58 g C4H10
• 2) Moles reactant ? Moles product
• 0.0172 mol C4H10 x 8mol CO2 0.0688 moles
  CO2
• 2 mol C4H10
• 3) Moles product ? Grams product
• 0.0688 mol x 44.0 g CO2 3.03 g CO2
• 1 mol
  CO2

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Homework

• 3.57-3.60 3.63-3.64 on pages 114-115