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Transcript

  • 1. Stoichiometry
  • 2. You already know... In a balanced equation the coefficients are MOLES. 2H 2 + O 2 -> 2H 2 O 2 moles Hydrogen, 1 mole Oxygen, 2 moles H 2 O How to Calculate Molar Mass: H 2 O = H 2 x 1.01 = 2.02 O 1 x 16.00 = 16.00 18.02 g/mol 1 mole of anything is 22.42 L examples: 1 mole water = 22.42 L 1 mole H 2 SO 4 = 22.42 L 1 mole acetic acid = 22.42 L
  • 3. Before the Math
    • Balance the equation.
      • You need the coefficients.
    • Look at what numbers the question provides.
      • Start with the number given.
    • Look at what the question is asking for.
      • This is where you stop.
      • It is also the correct label.
  • 4. The Math
    • Step 1: Get to the mole.
    • Step 2: Mole to mole ratio from the balanced equation.
    • Step 3: Use the mole to get to what you want.
    • *KEEP LIKE TERMS DIAGONAL.
  • 5. Finding Moles (this is going to be the first step in all the other types of problems)
    • How many moles of oxygen are formed if 1.34 moles of H 2 O 2 completely decomposes?
    • 1) Write and balance:
    • 2H 2 O 2 -> 2H 2 O + O 2 2:2:1
    • 2) Do the math
    = .67 mol O 2 1.34 mol H 2 O 2 (from the problem) 1 mol O 2 (from equation) 2 mol H 2 O 2 (from equation)
  • 6. Finding Liters
    • If I produce 2.4 L of oxygen in the decomposition of H 2 O 2 , how many L of H 2 O 2 did I start with?
    • 1) Write and balance:
    • 2H 2 O 2 -> 2H 2 O + O 2 2:2:1
    • 2) Do the math:
    = 4.8 L H 2 O 2 2.4 L O 2 1 mol O 2 2 mol H 2 O 2 22.42 L H 2 O 2 22.42 L O 2 1 mol O 2 1 mol H 2 O 2
  • 7. Finding Grams
    • In the decomposition of H 2 O 2 , how many grams of H 2 O 2 are required to produce 3.7g of water?
    • 1) Write and balance: 2H 2 O 2 -> 2H 2 O + O 2 2:2:1
    • 2) Because it is grams you need molar masses:
    • O 2 = 32.00 g/mol, H 2 O = 18.02 g/mol, H 2 O 2 = 34.02 g/mol
    • 3)Do the math.
    = 7.02 g H 2 O 2 3.7 g H 2 O 1 mol H 2 O 2 mol H 2 O 2 34.02 g H 2 O 2 18.02 g H 2 O 2 mol H 2 O 1 mol H 2 O 2
  • 8. Grams to Liters? The mole allows for any calculation.
    • In the decomposition of H 2 O 2 , how many L of H 2 O 2 are required to produce 1.5 g of water?
    • 1) Write and balance: 2H 2 O 2 -> 2H 2 O + O 2 2:2:1
    • 2) Do the math:
    = 1.87 L H 2 O 2 1.5 g H 2 O 1 mol H 2 O 2 mol H 2 O 2 22.42 L H 2 O 2 18.02 g H 2 O 2 mol H 2 O 1 mol H 2 O 2