CHEM 101 1nd Edition Lecture 10Outline of Last Lecture I. Formula and Molecular WeightsII. Chemical FormulasIII. Chemical Reactions and Conservation of MassIV. Hydrated CompoundsOutline of Current Lecture I. Chemical ReactionsII. Chemical EquationsIII. Balancing EquationsIV. Calculations Based on Chemical EquationsV. Chemical EquilibriumVI. Aqueous SolutionsCurrent LectureI. Chemical Reactionsa. Chemical reactions must always be balance - matter can neither be created nor destroyedi. Reactants are always on the lefii. Products are always on the rightb. Arrow indicates that reactants are changed into productsc. Numbers in front of molecules are stoichiometric coefficientsd. Symbols of States of Matter:i. Solid (s)ii. Gas (g)iii. Liquid (l)iv. Aqueous (aq)1. Dissolved in Watere. Ex: Ch4(g) + 2 O2(g) --> CO2(g) + 2 H2O(g)II. Chemical Equationsa. 4 Al(s) + 3 O2(g) --> 2 Al2O3(s)i. This equation means 4 Al atoms + 3 O2 molecules give 2 "molecules" of Al2O31. Not truly a molecule because it forms a latticeii. This equation means 4 moles of Al + 3 moles of O2 give 2 moles Al2O3These 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.b. Combustionsi. The burning (combustion) of a duel in oxygen is accompanied by the evolution of energyii. You are familiar with combustion reactions such as the burning of octane C8H18 in an automobile engine. 1. To balance:a. 1. Cb. 2. H divided by 2c. 3. O2. 2 C8H18(l) + 25 O2(g) --> 18 H2O(g) + 16 CO2(g)a. Because you would end up with 25/2 this entire formula is multiplied by 2 since you can't have half a moleculeiii. Rules to Remember1. Formulas for reactants and products must be correct, or the equation is meaningless.2. Subscripts in the formulas and the reactants can't be changed to suit numbers.III. Balancing Equationsa. Problem: Write the balanced equation for the complete combustion of propane C3H8i. Step 1: Write correct formula for the reactant and products1. Count the Carbons, then total the Hydrogens2. C3H8(g) + O2(g) --> CO2(g) + H2O(l)ii. Step 2: Balance the C atoms1. Leave the oxygen atom until the end (found in more than one product)iii. Step 3: Balance the H atomsiv. Step 4: Balance the O atomsv. Step 5: Verify that the number of atoms of each element is balanced1. C3H8(g) + 5 O2(g) --> 3 CO2(g) + 4 H2O(l)b. Problem: Write a balanced equation for the combustion to give NO and H2Oi. Step 1: Write correct formulas for the reactants and the products1. NH3(g) + O2(g) --> H2O + NOii. Step 2: Balance the N atomsiii. Step 3: Balance the H atoms1. 2 NH3 + O2 --> 3 H2O + 2 NOiv. Step 4: Balance the O atoms1. 3+2= 5/2, oops!, multiply by 2 = 52. 4 NH3 + 5 O2 --> 6 H2O + 4 NOIV. Calculations Based on Chemical Equationsa. Chemical equations represent very precise languageb. Possible to extract a large amount of informationc. Consider Reaction:i. Fe2O3 + 3 CO --> 2 Fe + 3 CO2d. For every mole (or formula unit) of iron (III) oxidei. 3 moles (molecules) of carbon monoxide are needed to form:1. 2 moles (atoms) of Fe 2. 3 moles (atoms) of CO2e. Equation relates moles and molecules (not mass) by the stoichiometric coefficientsi. Fe2O3 + 3 CO --> 2 Fe + 3 CO21. If there are 2 formula units of Fe2O3, how much CO is need? 6 molecules2. If there are 9 moles of CO, how much CO2 can be formed? 9 moles3. If 8 atoms of Fe are formed, how much CO wad needed? 12 moleculesV. Chemical Equilibriuma. When balancing factions, we assumed the reactions were converted totally into productsb. Most reactions do NOT go completely to productsc. Instead they go to equilibriumi. Mixture of reactants and productsii. Reversible: at equilibrium, reacts convert to products just as fast as products convert to reactantsiii. Product favored: reacts turn mostly to productsiv. Reactant favored: products turn mostly to reactsv. Use double arrows to symbolize equilibriumvi. Rates of forward and backwards reactions are always equalVI. Aqueous Solutionsa. Solutioni. Homogenous mixture of tow or more substancesii. Solutions may be liquid, solid, or gasb. Solventi. Substance present in the greatest quantityc. Solutei. Substance other than the solvent.ii. Solutes are said to be dissolved in the solventd. Aqueous Solution (aq)i. A liquid solution in which the solvent is watere. Many reactions take place in aqueous solutions.i. Water is ofen referred to as the universal solvent.f. It is therefore important to know what happens to substance when they are places in water.i. Is it soluble in water?ii. If it is soluble, does it break up into ions?g. A compound that dissolves in water to an appreciable extent is soluble, in not it is insoluble.h. Example: CH3OHi. Soluble in water, but does not break into ions the water adds the