Chem week 3 Ch.3 notes
Chem week 3 Ch.3 notes CHEM 211-002
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This 3 page Class Notes was uploaded by Briana Marcy on Friday September 25, 2015. The Class Notes belongs to CHEM 211-002 at George Mason University taught by Paul Cooper in Summer 2015. Since its upload, it has received 63 views. For similar materials see General Chemistry 1 in Chemistry at George Mason University.
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Date Created: 09/25/15
Briana Marcy CHEM 211 Dr Cooper Lecture Notes Week 3 Ch 3 Chapter 3 A mole mol is the amt of a substance that contains the same number of quotentitiesquot as there are atoms in exactly 12g of carbon 12 Entities atoms ions molecules formula units or electrons any type of particle One mole contains 6022x10quot23 entities to 4 sig figs This number is called Avogadro s number and is abbrev N EXAMPLES 1 atom of Fe has the mass 5585amu 1 mol of Fe has mass 5585g And 1 molecule of H20 has mass 1802 amu 1 mol of H20 has mass 1802g Molar Mass is the mass per mole of its entities For monatomic elements the molar mass is the same as the atomic mass in gramsmole the atomic mass is found on the Per Table Ex Molar mass of Ne2018 gmol Mass Percent from the chemical formula See slide 310 Many of the formula problems will need to just be practiced practice practiced See PP slides for some the book for others and YouTube is helpful for some concepts as well Mass Percent and Mass of an Element Mass percent can be used to calc the mass of a particular element in any mass of a compound see slide 313 for formula Empirical and Molecular Formulas Purpose to show the ratios The empirical formula is the simplest formula for a compound that agrees w the elemental analysis It shows the lowest whole of moles and gives the relative of atoms for each element present Ex Emp Formula for hydrogen peroxide is H0 The molecular formula shows the ACTUAL of atoms for each element in a molecule of the compound Ex Molec formula for hy perox Is H202 s in right subscripts Determining the Molecular Formula The molecular formula gives the actual numbers of moles of each element present in 1 mol of compound The molecular formula is a wholenumber multiple of the empirical formula Chemical Equations A chemical equation uses formulas to express the identities and quantities of substances involved in a physical or chemical change Stoichiometric Calculations The coefficients in a balanced chemical equation Represent the relative number of reactant and product particles and the relative number of moles of each Since moles are related to mass The equation can be used to calculate masses of reactants andor products for a given reaction The mole ratios from the balanced equation are used as conversion factors Reactions in Sequence Reactions often occur in sequence The product of one reaction becomes a reactant in the next An overall reaction is written by combining the reactions Any substance that forms in one reaction and reacts in the next can be eliminated Limiting Reactants So far we ve assumed that reactants are present in the correct amounts to react completely In reality one reactant may limit the amt of product that can form The limiting reactant will be completely used up in the reaction The reactant that Is not limiting is in excess some of this reactant will be left over Reaction Yields The theoretical yield is the amount of product calculated using the molar ratios from the balanced equation The actual yield is the amt of product actually obtained The actual yield is usually less than the theoretical yield Solution Stoichiometry Many reactions occur in solution A solution consists of one or more solutes dissolved in a solvent The concentration of a solution is given by the quantity of solute present is a given quantity of solution MOLARITY M is often used to express concentration
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