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VI. Organic Compounds = carbon containing compounds A. Hydrocarbons = only carbon and hydrogen. cinnamaldehyde. B. Functionalized Hydrocarbons = contain other elements + C + H. I. Chemical Stoichiometry [Chapter 4.1-4.3]
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VI. Organic Compounds = carbon containing compounds • A. Hydrocarbons = only carbon and hydrogen cinnamaldehyde
B. Functionalized Hydrocarbons = contain other elements + C + H
I. Chemical Stoichiometry [Chapter 4.1-4.3] • A. Balanced equations provide the relationship between the relative numbers of reacting molecules and product molecules • 2 CO + O2 2 CO2 • 2 CO molecules react with 1 O2 molecules to produce 2 CO2 molecules • 2 moles CO molecules react with 1 mole O2 molecules to produce 2 moles CO2 molecules • Since moles can be converted to masses, we can determine the mass ratio of the reactants and products as well • 2 moles CO = 1mole O2 = 2 moles CO2 • 1 mole CO = 28.01 g, 1 mole O2 = 32.00 g, and 1 mole CO2 = 44.01 g • 2(28.01) g CO = 1(32.00) g O2 = 2(44.01) g CO2 • Procedure for calculating Masses of Reactants and Products in Reactions • Write a balanced equation for the reaction • Convert the known mass of a given reactant or product to moles • Use the balanced equation to find the moles of the unknown compound • Convert the moles of unknown to grams of unknown
Example: Determine the number of grams of Carbon Monoxide required to react with 48.0 g Oxygen, and determine the mass of Carbon Dioxide produced • 1. Write the balanced equation • 2 CO + O2 2 CO2 • 2. Use the coefficients to find the mole relationship • 2 moles CO = 1 mol O2 = 2 moles CO2 3. Determine the Molar Mass of each • 1 mol CO = 28.01 g • 1 mol O2 = 32.00 g • 1 mol CO2 = 44.01 g 4. Use the molar mass of the given quantity to convert it to moles • 5. Use the mole relationship to convert the moles of the given quantity to the moles of the desired quantity
Use the molar mass of the desired quantity to convert the moles to mass • Example: What mass of O2 will react with 96.1g of propane (C3H8)? • Example: Lithium hydroxide absorbs carbon dioxide to form lithium carbonate and water. How much CO2 can be absorbed by 1.00 kg LiOH? C3H8 + 5O2 -------> 3CO2 + 4H2O
Limiting and Excess Reactants • Definitions • A reactant which is completely consumed is called a limiting reactant • A reactant not completely consumed in a reaction is called an excess reactant • The maximum amount of a product that can be made when the limiting reactant is completely consumed is called the theoretical yield • Example: CH4 + H2O -------> 3H2 + CO • 1. The stoichiometry is supposed to be 1:1 for methane and water • Water is the limiting reactant • Methane is the excess reactant • The theoretical yield is 9H2 • The theoretical yield is 3CO
C. Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide 1. Write the balanced equation • 2 CO + O2 2 CO2 2. Use the coefficients to find the mole relationship • 2 moles CO = 1 mol O2 = 2 moles CO2 3. Determine the Molar Mass of each • 1 mol CO = 28.01 g • 1 mol O2 = 32.00 g • 1 mol CO2 = 44.01 g • Determine the moles of each reactant • 5. Determine the number of moles of reactant A needed to react with reactant B
Compare the calculated number of moles of reactant A to the number of moles given of reactant A • If the calculated moles is greater, then A is the Limiting Reactant; if the calculated moles is less, then A is the Excess Reactant • The calculated moles of O2 (1.00 moles) is less than the given 1.50 moles, therefore O2 is the excess reactant • Use the limiting reactant to determine the moles of product, then the mass of product • 25.0 kg N2 and 5.00 kg H2 are reacted to make how much NH3? • N2(g) + 3H2(g) -------> 2NH3(g)
827 mol N2 are needed and we are given 893 mol N2 • H2 is the limiting reagent • N2 is the excess reagent • Calculate the amount of product formed from the limiting reagent
Actual Yield Theoretical Yield Percent Yield = x 100% • Percent Yield • Most reactions do not go to completion • The amount of product made in an experiment is called the actual yield • The percentage of the theoretical yield that is actually made is called the percent yield • Example: CO and H2 combine to form CH3OH. What is the theoretical yield of CH3OH if 68.5 kg CO and 8.60 kg H2 were reacted? What is the percent yield if 35.7 kg was the actual yield of CH3OH? • 1. CO + 2H2 -------> CH3OH
2,135 mol CO are needed and we are given 2,440 mol CO • H2 is the limiting reagent • CO is the excess reagent • Calculate the amount of product formed from the limiting reagent • The Theoretical Yield of CH3OH is 68.6 kg • The Percent Yield of CH3OH = ?