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Stoichiometry

Stoichiometry. Chapter 9. Stoichiometry. The Proportional relationship between two or more substances during a chemical reaction. Definitions. Limiting Reactant – What gets used up in the chemical reaction Excess Reactant – Chemical that is used in a reaction but some is left over.

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Stoichiometry

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  1. Stoichiometry Chapter 9

  2. Stoichiometry The Proportional relationship between two or more substances during a chemical reaction.

  3. Definitions Limiting Reactant – What gets used up in the chemical reaction Excess Reactant – Chemical that is used in a reaction but some is left over

  4. 4 Simple rules 1. Write Down the Given 2. Convert to moles 3. Use the mole ratio 4. Convert to desired units

  5. 4 Simple rules 1. Write Down the Given You need to know what you start with and what you need to end with.

  6. 4 Simple rules 2. Convert to moles One MOLE # of particle units Volume Mass Molar Mass from periodic table 22.4 L 6.02 x 1023atoms, molecules, or formula units

  7. 4 Simple rules 3. Use the mole ratio The mole ratio comes from the coefficients in a balanced Chemical Equation Where does the mole ratio come from?

  8. 4 Simple rules 3. Use the mole ratio Fe2O + 2 Li Li2O + 2 Fe What is the ratio between Fe and Fe2O?

  9. 4 Simple rules 3. Use the mole ratio Fe2O + 2 Li Li2O + 2 Fe What is the ratio between Fe and Li?

  10. 4 Simple rules 3. Use the mole ratio The coefficients can represent # of moles or # of molecules.

  11. 4 Simple rules 4. Convert to desired units If grams are desired use mass from P.T. If you need liters use 22.4L If you need atoms or molecules 6.02 x 1023 If moles are what is needed you are already done.

  12. Convert to desired unit. Grams from Periodic Table if mass 22.4 L if volume 6.02 x 1023 atoms/molecule Mole ratio of desired compound from the balanced equation. 1 mole of (starting element/ molecule) Write Down the given 1 mole of (ending element/ molecule) Mole ratio of given from balanced equation. Grams from Periodic Table if mass 22.4 L if volume 6.02 x 1023 atoms/molecules

  13. Example • If you have two givens it is a limiting reactant problem, solve both givens for their product. The smallest answer is the correct answer! • How many grams of Cu can be formed when 167.4 g of Fe reacts with 399.2 g of CuCl2? 2 Fe + 3 CuCl2 3 Cu + 2FeCl3

  14. 2 Fe + 3 CuCl2 3 Cu + 2FeCl3

  15. How many grams of excess are left over from problem #1? The math shows that you needed 110.4 g of Fe (2 moles Fe). Since you started with 167.4g Fe, all you need to do is subtract the two in order to find out how much excess you have. 167.4 g Fe (Given) -110.4 g Fe (Needed) 57.0 g Fe excess

  16. Finding % yield • Actual Yield x 100% = % yield Theoretical Yield • Actual Yield must be found experimentally. You must do the experiment yourself or they must give the information to you. You will see words like produced and formed in a problem that is giving you the actual yield. • Theoretical Yield is done using stoichiometry. You would take the given and find out how much of a product should be formed. It is a prediction and will always be done using math.

  17. The End

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