chemistry_chapter4notes

chemistry_chapter4notes - Ex. The balanced equation for the...

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Ex. The balanced equation for the combustion of methane is: CH 4 ( g ) + 2 O 2 ( g ) CO 2 ( g ) + 2 H 2 O( l ) If we start out with 5 CH 4 molecules and 8 O 2 molecules, what is our limiting reactant? What is our theoretical yie We first calculate the number of CO 2 molecules that can be made from 5 CH 4 molecules: We then calculate the number of CO 2 molecules that can be made from 8 O 2 molecules: O 2 is the limiting reactant and 4 CO 2 molecules is the theoretical yield. The CH 4 is in excess. Chapter 4: Chemical Quantities and Aqueous Reactions 4.1 Global Warming and the Combustion of Fossil Fuels greenhouse gases – gases that act like the glass of a greenhouse, allowing sunlight to enter the atmosphere and warm Earth’s surface, but preventing some of the heat generated by the sunlight from escaping. The balance between incoming and outgoing energy from the sun then determines Earth’s average temperature. Without greenhouse gases in the atmosphere, more heat energy would escape and Earth’s average temperature would be about 60 °F colder than it is now If the concentration of greenhouse gases in the atmosphere were to increase, Earth’s average temperature would rise In recent years the amount of atmospheric carbon dioxide (CO 2 )—Earth’s most significant greenhouse gas in terms of its contribution to climate—is rising Enhances the atmosphere’s ability to hold heat and may therefore lead to global warming o global warming – an increase in Earth’s average temperature probably due to the burning of fossil fuels 4.2 Reaction Stoichiometry: How Much Carbon Dioxide? Stoichiometry – the numerical relationships between chemical amounts in a balanced chemical equation allows us to predict the amounts of products that will form in a chemical reaction based on the amounts of reactants that undergo the reaction allows us to determine the amount of reactants necessary to form a given amount of product Making Molecules: Mole-to-Mole Conversions Balanced equation for combustion of octane: 2 C 8 H 18 ( l ) + 25 O 2 ( g ) 16 CO 2 ( g ) + 18 H 2 O( g ) From this equation we can write the following stoichiometric ratio: 2 mol C 8 H 18 ( l ) : 16 mol CO 2 ( g ) Suppose that we burn 22.0 moles of C 8 H 18 ; how many moles of CO 2 are produced? Making Molecules: Mass-to-Mass Conversions General Conceptual Plan: Page | 1
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4.3 Limiting Reactant, Theoretical Yield, and Percent Yield limiting reactant – the reactant that limits the amount of product in a chemical reaction reactant in excess – any reactant that occurs in a quantity greater than that required to completely react with the limiting reactant theoretical yield – the amount of the product that can be made in a chemical reaction based on the amount of limiting reactant actual yield – the amount of product actually produced by a chemical reaction o always equal to or less than the theoretical yield because a small amount of product is
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chemistry_chapter4notes - Ex. The balanced equation for the...

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