INTRO TO STOICHIOMETRY EQ How do we use

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INTRO TO STOICHIOMETRY EQ: How do we use the mole ratio of balanced equations

INTRO TO STOICHIOMETRY EQ: How do we use the mole ratio of balanced equations to solve stoichiometry problems?

MOLE RATIOS 2 H 2 + O 2 → 2 H 2 O The

MOLE RATIOS 2 H 2 + O 2 → 2 H 2 O The mole ratio is the relationship of the number of moles of the chemicals that participate in a chemical equation. For ex: For every 2 moles of hydrogen we can get 2 moles of water. For every one mole of oxygen we can get 2 moles of water. For every two moles of hydrogen we need one mole of oxygen.

MOLE RATIOS 2 H 2 + O 2 → 2 H 2 O We

MOLE RATIOS 2 H 2 + O 2 → 2 H 2 O We can also say: 2 moles of H 2 = 2 moles of H 2 O 1 mole of O 2 = 2 moles of H 2 O 2 moles of H 2 = 1 mole of O 2 What can we do with things equal to each other? CONVERSION FACTORS!!!

STEPS TO CALCULATE STOICHIOMETRIC PROBLEMS 1. Correctly balance the equation. 2. Convert the given

STEPS TO CALCULATE STOICHIOMETRIC PROBLEMS 1. Correctly balance the equation. 2. Convert the given amount into moles. 3. Set up mole ratios. 4. Use mole ratios to calculate moles of desired chemical. 5. Convert moles back into final unit.

MASS-MASS PROBLEM: 6. 50 grams of aluminum reacts with an excess of oxygen. How

MASS-MASS PROBLEM: 6. 50 grams of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed? 4 Al + 3 O 2 2 Al 2 O 3 6. 50 g Al 1 mol Al 2 O 3 101. 96 g Al 2 O 3 26. 98 g Al 4 mol Al 1 mol Al 2 O 3 (6. 50 x 1 x 2 x 101. 96) ÷ (26. 98 x 4 x 1) = = ? g Al 2 O 3 12. 3 g Al 2 O 3 are formed

ANOTHER EXAMPLE: • If 10. 1 g of Fe are added to a solution

ANOTHER EXAMPLE: • If 10. 1 g of Fe are added to a solution of Copper (II) Sulfate, how many grams of solid copper would form? 2 Fe + 3 Cu. SO 4 ® Fe 2(SO 4)3 + 3 Cu Answer = 17. 2 g Cu

HOW DO YOU GET GOOD AT THIS?

HOW DO YOU GET GOOD AT THIS?

VOLUME-VOLUME CALCULATIONS: • How many liters of CH at STP are required to completely

VOLUME-VOLUME CALCULATIONS: • How many liters of CH at STP are required to completely react 4 4 with 17. 5 L of O ? 2 2 CH 4 + 2 O 2 ® CO 2 + 2 H 2 O 1 mol O 2 1 mol CH 4 22. 4 L CH 4 17. 5 L O 2 22. 4 L O 2 2 mol O 2 1 mol CH 4 = 8. 75 L CH 4 Notice anything relating these two steps?

AVOGADRO TOLD US: • Equal volumes of gas, at the same temperature and pressure

AVOGADRO TOLD US: • Equal volumes of gas, at the same temperature and pressure contain the same number of particles. • Moles are numbers of particles • You can treat reactions as if they happen liters at a time, as long as you keep the temperature and pressure the same. 1 mole = 22. 4 L @ STP

SHORTCUT FOR VOLUME-VOLUME? • How many liters of CH 4 at STP are required

SHORTCUT FOR VOLUME-VOLUME? • How many liters of CH 4 at STP are required to completely react with 17. 5 L of O 2? CH 4 + 2 O 2 ® CO 2 + 2 H 2 O 17. 5 L O 2 1 L CH 4 2 L O 2 = 8. 75 L CH 4 Note: This only works for Volume-Volume problems.