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Chemical Quantities

Chemical Quantities. CHM 108 Suroviec Spring 2014. I. Reaction Stoichiometry. Given the recipe for 16 pancakes: 2 cups flour 2 teaspoons baking powder 2 eggs 1 cup milk. I. Reaction Stoichiometry. For molecule we have the balanced chemical equation. A. Mass to Mass Conversions.

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Chemical Quantities

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  1. Chemical Quantities CHM 108 Suroviec Spring 2014

  2. I. Reaction Stoichiometry • Given the recipe for 16 pancakes: • 2 cups flour • 2 teaspoons baking powder • 2 eggs • 1 cup milk

  3. I. Reaction Stoichiometry • For molecule we have the balanced chemical equation

  4. A. Mass to Mass Conversions • The question when synthesizing a compound is how much will this reaction make • Using the balanced chemical equation we can answer that. CaF2 + H2SO4 CaSO4 + 2HF

  5. II. Limiting Reagents • When carrying out a reaction it is often the case that the reactants are not in exact stoichiometric amounts • One will always be used up first: limiting reagent • One will always be in excess: excess reagent C6H12O6 (s) + 6O2(g)  6CO2 (g) + 6H2O (l)

  6. A. Limiting Reactant, Theoretical Yield and Percent Yield • In the lab we often want to know how much product can be made (theoretical yield) vs. how much we actually made (percent yield) 2Ca(s) + O2(g)  2CaO (s) If you start with 43.8g of Ca(s) and 32.5g of O2 what is the limiting reagent and theoretical yield?

  7. Example • Now lets say you did this same reaction (previous slide) and produced 57.42 grams of CaO. What was the percent yield?

  8. IV. Solution Concentration and Stoichiometry • Working with aqueous solutions is very common in the lab so we need to look at how they are prepared and used. • Solution • Solvent • Solute

  9. A. Solution Concentration • Molarity is defined as moles/Liter • If 15.5g of Na2CO3 is dissolved into water to make 1.50L, what is the molarity?

  10. B. Using molarity • How many grams of glucose, C6H12O6, are needed to make a 2.00L solution of 0.750M?

  11. C. Dilution • HCl comes as a 12M solution, but the experiment calls for 500 mL of 0.100M. How will you make this?

  12. D. Solution Stoichiometry • What volume (in mL) of a 0.150M HNO3 solution is required to completely react with 37.7 mL of a 0.110 M Na2CO3 solution according to the equation below? Na2CO3 (aq) + 2HNO3(aq)  2NaNO3 (aq) + CO2(g) + H2O (l)

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