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Stoichiometry Chapter 12

Stoichiometry Chapter 12. Stoichiometry. STOY-KEE-AHM-EH-TREE Founded by Jeremias Richter, a German chemist Greek orgin stoikheion – element & metron – measure

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Stoichiometry Chapter 12

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  1. StoichiometryChapter 12

  2. Stoichiometry • STOY-KEE-AHM-EH-TREE • Founded by Jeremias Richter, a German chemist • Greek orgin • stoikheion – element & metron – measure • The branch of chemistry that deals with the quantities of substances that enter into, and are produced by, chemical reactions.  • Shows the quantitative relationship between reactants and products in a chemical reaction. • How much product is formed from a given amount of reactants.

  3. Balanced Chemical Equation (BCE) • Coefficientsare used to balance chemical equations. • The BCE illustrates that chemical reactions follow Law of Conservation of Mass • The number and types of atoms on the reactants side is equal to the number and types of atoms on the products. • Reactants (left)Products (right) • The coefficients are molar ratios of reactants and products. • We can use the molar ratios to convert from one substance to another using Stoichiometry

  4. Stoichiometry Problems • Each problem will be 3 steps • 2. Mole to mole ratio using balanced chemical equation (BCE) • 1. Convert to moles • 3. Convert to required unit. BCE

  5. Example • What is the mass of Al2O3 that can be made from 25 grams of aluminum? • Balanced Equation: 4 Al + 3 O2 2 Al2O3 BCE

  6. You Should Know About Stoichiometry • You have to use units to understand the process • Units include g, mol, L, particles AND chemical formulas • Convert your given to moles • You have to use units to understand the process • Use BCE coefficients to convert from one substance to another • You have to use units to understand the process • Convert answer to required unit • You have to use units to understand the process • Units include g, mol, L, particles AND chemical formulas • It is not that hard 

  7. Percent Yield • Indicates the percent of theoretical yield that was obtained from the final product in an experiment.  • The closer to 100% the better • Percent Yield = actual mass x 100 theoretical mass

  8. Percent Error • Percent Error = (actual mass – theoretical mass) x 100 theoretical mass • The lower the percent error the better

  9. Limiting Reactants • The limiting reactant is the reactant present in the smallest stoichiometric amount • In other words, it’s the reactant you’ll run out of first Hydrogen is limiting Hydrogen is limiting 5N2 and 9H2 6NH3 and 2N2

  10. How 2 Calculate the Limiting Reactant • Convert each of the given reactants to a product • The reactant that produces the least product is the limiting reactant. Example: • Nickel replaces silver from silver nitrate in solution according to the following equation: 2AgNO3 + Ni → 2Ag + Ni(NO3)2 If you have 22.9 g of Ni and 112 g of AgNO3 ,what mass of nickel(II) nitrate would be produced? • 22.9g Ni x 1 mol Ni x 1 mol Ni(NO3)2x 182.7g Ni(NO3)2 = 71.3 g Ni(NO3)2 58.7g Ni 1 mol Ni 1 mol Ni(NO3)2 • 112 g AgNO3 x 1 mol AgNO3 x 1 mol Ni(NO3)2x 182.7g Ni(NO3)2 = 60.2 g Ni(NO3)2 169.9g AgNO3 2 mol AgNO3 1 mol Ni(NO3)2 • AgNO3 is limiting & 60.2 g Ni(NO3)2 can be produced

  11. Limiting Reactant Challenge • Given 20 mLHCl (1.46g HCl) calculate the amount of Mg to add to generate the maximum production of Hydrogen gas with Mg still limiting the reaction. • Calculate the percent yield of Hydrogen gas

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