CHEM 101 1st Edition Lecture 7 Outline of Last Lecture I. Formulas and Names of Molecular CompoundsII. The MoleIII. Percent CompositionIV. Empirical FormulaV. HydratesOutline of Current Lecture I. Introduction to Chemical Reactions and EquationsII. Introduction to the Chemical EquilibriumIII. Aqueous SolutionsIV. Test ReviewCurrent LectureChapter 3: Chemical Reactions- Introduction to Chemical Reactions and Equationso A chemical reaction involves a rearrangement and or a change in oxidation state of atoms (transfer of valence electrons) from reactants to products.o Evidence of a chemical reaction Gas evolution Temperature change Color change Precipitation (insoluble species forms)o Example for how to describe a chemical reaction: Reactants: Zn(s) +I2(s) Products: ZnI2(s) (Zinc Iodide) + (energy)*It is important to have a balanced chemical equation because of the Law of Conversion of Matter which states that matter can neither be created nor destroyed.o 4 Al(s) + 3 O2(g) 2Al2O3(s) * The leading numbers are called stoichiometric coefficients they represent how many moles of Al (in this example) we need to react with how ever many moles of O2 to make 2 moles of 2Al2O3 These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. This equation states that 4 Al atoms + O2 molecules react to form 2 formula units of 2Al2O3 Or… 4 moles of Al + 3 moles of O2 react to form 2 moles of 2Al2O3o Ex: C2H6 + O2 CO2 + H2O 1. Find the missing stoichiometric coefficients2C2H6 + 7O2 4CO2 + 6H2O- Clicker Question: The unbalanced equation describing the oxidation of propane is __C3H8(g) + __O2(g) CO2(g) + __H2O(g)o A. 1,5,3,4 (correct answer)B. 2,4,5,3 C. ½,7,2,5D. 3, 1, ½, 3- Introduction to the Chemical Equilibrium Reactants Products N2(g) + 3H2(g) 2NH3(g)o In this case, we also need to consider the reverse reaction:2NH3(g) N2(g) +3H2(g)o The reaction and then be indicated as a so-called equilibrium reaction (with a double arrow:N2(g) + 3H2(g) 2NH3(g)o Once an equilibrium is achieved, the reaction continues, but there is no net change in the amounts of products or reactantso Chemical reactions always proceed spontaneously toward equilibriumreactants productso Once an equilibrium is established, we can recognize if the reaction is product-favored (after the reaction is over, there are more products than reactants) or reactantfavored (after the reaction is over, there are more reactants than products).- Aqueous SolutionsSolution = Solute + Solvento Solute- the substance which is dissolved (smaller amount)o Solvent- the substance that dissolves (larger amount)o In aqueous solutions water is the solvento Compounds whose aqueous solutions conduct electricity are called electrolytes.o All ionic compounds that are water-soluble, are also electrolyteso We distinguish between strong, weak, and non-electrolytes: Strong Electrolyte: number of charged particles are high. Completely dissociates in a solution- NaCl(s) Na^(+)(aq) + Cl^(-)(aq) Weak Electrolyte: number of charged particles are low. Very little dissociated in a solution- HAc(aq) + H2O(l) -->Ac^(-)(aq) + H3O^(+)(aq) Non Electrolyte: no charged particles. Very little to no dissociation in a solution.- C2H5OH(l) C2H5OH(aq)- Test 1 Guidelineso Seating chart on elearning/ outside the door on test dayo Bring your ID, a pencil, and a non programmable calculator. A scantron will be provided.o Has 20 multiple choice questions Tricky bubbling, read directions on elearning!!o Focus on lecture notes first then textbook exercises. Then
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