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Unit 4: Stoichiometry

Unit 4: Stoichiometry. Stoichiometry. Chemical Equations and the Mole. Remember: a chemical equation is like a recipe – it tells you the ingredients (reactants) you need to make certain products chemical equations tell you the relative quantities of reactants and products in a reaction.

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Unit 4: Stoichiometry

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  1. Unit 4: Stoichiometry Stoichiometry

  2. Chemical Equations and the Mole • Remember: • a chemical equation is like a recipe – it tells you the ingredients (reactants) you need to make certain products • chemical equations tell you the relative quantities of reactants and products in a reaction

  3. Chemical Equations and the Mole How many moles do you have of each of the following? Frame (F): Seat (S): Wheel (W): Handlebar (H): Pedal (P): Tricycle (FSW3HP2): 1 mole 1 mole 3 moles 1 mole 2 moles 1 mole

  4. Chemical Equations and the Mole Example: If you had 4 moles of S and an excess of all the other reactants, how many tricycles (FSW3HP2) could you make? We can apply the tricycle example to chemical reactions.

  5. Stoichiometry Stoichiometry:Using a known amount of one substance to predict how much of a reactant will be used or how much of a product will be produced. You can use stoichiometry to answer questions like: Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen. N2 + H2 → NH3

  6. Stoichiometry – The Box Method Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen. N2 + 3H2 → 2NH3 Step 1: Balance the equation.

  7. Stoichiometry – The Box Method Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen. N2 + 3H2 → 2NH3 Step 2: Construct the box and fill in known information (starting amount and molar masses).

  8. Stoichiometry – The Box Method Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen. N2 + 3H2 → 2NH3 MOREx 2/1 Step 3: Calculate missing information until you determine what the problem is asking you to find.

  9. Stoichiometry – The Box Method Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen. N2 + 3H2 → 2NH3 MOREx 2/1 Step 3: Calculate missing information until you determine what the problem is asking you to find.

  10. Stoichiometry – Practice! How many grams of water would be produced from 60 grams of H2 and an excess of O2? __H2 + __O2 → __H2O

  11. Stoichiometry You can use stoichiometry to answer questions like: Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. N2 + H2 →NH3 • Steps: • Balance the equation. • Convert mass to moles. • 3. Convert moles of ‘known’ to moles of ‘unknown’ using the mole ratios (coefficients) from the balanced equation. • 4. Convert moles of ‘unknown’ to mass ‘unknown’.

  12. Stoichiometry – Step 1 Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. N2 + H2 →NH3 Step 1: Balance the equation.

  13. Stoichiometry – Step 2 Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. N2 + H2 →NH3 Step 2: Convert mass to moles.

  14. Stoichiometry – Step 3 Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. N2 + H2 → NH3 Step 3: Convert moles of ‘known’ to moles of ‘unknown’ using the mole ratios (coefficients) from the balanced equation.

  15. Stoichiometry – Step 4 Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. N2 + H2 →NH3 Step 4: Convert moles of ‘unknown’ to mass ‘unknown’.

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