Chapter 3 Outline (Chang Textbook)
Chapter 3 Outline (Chang Textbook) Chem 1305
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This 3 page Class Notes was uploaded by Jonathan A Delgado on Friday October 2, 2015. The Class Notes belongs to Chem 1305 at University of Texas at El Paso taught by James E. Becvar in Summer 2015. Since its upload, it has received 97 views. For similar materials see general chemistry in Chemistry at University of Texas at El Paso.
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Date Created: 10/02/15
Chapter 3 Mass Relationships in Chemical Reactions Notetaker Jonathan Delgado 09302015 Section 31 Atomic Mass 0 Mass of an atom depends on electrons protonsand neutrons it contains 0 Atomic mass is the mass of the atom in atomic units amu 0 Atomic mass unit the mass of exactly equal to 112 of a carbon12 atom 6 gtAtomic C gtElement 1201 gtAtomic Mass o For some elements the atomic mass is an average of the element and its isotope Section 32 Avogadro39s and molar mass of an Element 0 Mole Mol the amount of a substance that contains as many elementary entities as their are atom exactly 12g or 0012kg of the carbon12 isotope o Avogadro39s number Na Na 60221415 x10quot23 or Na 6022 x 10quot23 Preferred o Molar mass is the mass in grams or kilograms of 1 mole of units such as atoms or molecules of a substance Section 33 Molar Mass 0 molecular mass molecular weight is the sum of atomic masses in amu in the molecule 0 molar mass of a compound in grams is numerically equal to its molecular mass in amu o for ionic compounds like NaCl and MgO do not contain discrete molecular units so the Formula Mass is used instead of Molar Mass Section 35 Percent Composition of compounds 0 Percent composition by mass percent by mass of each element in a compound Percent composition of an element n x molar mass of an elementmolar mass of compound x 100 Both the molecular and empirical formulas are different operations they both give the same answer for percent mass composition Section 3 6 Experimental Determination of Empirical Formulas The fact that we can format the empirical formula of a compound if we know the percent composition enables us to identify compounds experimentally Empirical based on only on observation The formula calculated from percent composition by mass is always the empirical formula because of the empirical formula because of the subscripts in the formula are always reduce to the smallest whole numbers Section 3 7 chemical reactions and chemical equations Chemical reaction a process in which a substance or substances is changed into one or more new substances Chemical equation chemical symbols to show what happens during a chemical reac on Reactants are the starting materials in a chemical equation Products are the substance that is produce Reactants gtgtgt Products Rules for Balancing Chemical Equation Identify all reactant and products and write their correct formulas on the left side and right side of the equation respectively Begin balancing the equation by trying different coefficients to make the number of atoms of each element the same on both sides of the equation change coefficients not subscripts Look for the elements that appear only once on each side of the equation with the same number of elements on each side Don t worry about those that are the same but balance the one that are not the same on each side Check your balance equation to make sure that you have the same number of elements on each side Section 3 8 Amounts of Reactants and Products Stoichiometry the quantity study of reactants and products in chemical reaction Mole Methodthe stoichiometric coefficients in a chemical equation can be interpreted as the number of moles of each substance Solving Stoichiometry Problems Write the balanced equation for the problem Convert the given amount of the reactant in grams or other units to number of moles use the mole ratio from the balanced equation to calculate the number of moles of product formed 4 convert the moles of product to grams or other units of product Section 3 9 Limiting Reagents o stoichiometric amounts proportions indicated by the balanced equations 0 limiting reagents the reactant that is used up first 0 excess reagent reactants present in quantities greater than necessary to react with quantity of the limiting reagent Section 310 Reaction Yield 0 Theoretical Yield the amount of product that would result if all the limiting reagent was used Actual Yield the amount of product that was obtained from a reaction Percent Yield the proportion of the Actual Yield to the Theoretical Yield Yield actual yield theoretical yield X 100
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