CH 101 Chapter 8 Notes!!
CH 101 Chapter 8 Notes!! CH 101
Popular in General Chemistry
Popular in Chemistry
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This 0 page Class Notes was uploaded by Allie Newman on Wednesday November 4, 2015. The Class Notes belongs to CH 101 at University of Alabama - Tuscaloosa taught by Professor John McDuffie in Fall 2015. Since its upload, it has received 61 views. For similar materials see General Chemistry in Chemistry at University of Alabama - Tuscaloosa.
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Date Created: 11/04/15
CHEM 101 CHAPTER 8 NOTES Climate Change and Combustion of Fossil Fuels l The Greenhouse Effect Greenhouse gases in the atmosphere Allow sunlight to enter the atmosphere Warm Earth s surface Prevent some of the heat generated by the sunlight from escaping The Ereenheuee Effect lmh hli Ell555595 ELIIE39IL39 I ll a39lliixi I iml rudinle ITllll i Illlil39iillllil39li ultlllltihl l l39len 39r quot mu Gregnheuw Ismllnlnuh HELLE is mlPljmi h ll39 39iim quot iliiri Infra aimingJ l 335quot git39 a1l1aLIie 31mm K TL It 1311 11 The balance between incoming and outgoing energy from the sun determines Earth s average temperature Global Warming Scientists have measured an average 06 C rise in atmospheric temperature since 1860 During the same period atmospheric C02 levels have risen 25 Are the two trends causal Atmecs haeric Earlier Dielxlide Gl ihal Tamper atmg 3gp 3 Fill quot 34 i 3e 1 351 quot galls 1 39 f ills 1 Run 9 31th f alm 39 394F Elli 7 rr v LE1 nnuel meat r feetM ruten l llx l 1 lquot 1154 in I ilkquot Earlarm L linxitle tencenlrutien lj lirrtgm n nllmn IIt39lillllt39FEHELIEI L Llr39lr ielliuni Hill I n4 l l l l I I IllFeel 133M Willi 11331 Bilill 39I39HL EI l El39H39U Ellllil Eilgll iiiHall lEl39lJIIEI WEE 12M ll 39 ll Mill EMU EUHJ39 quotFear 1E m u Physical Changes in Matter 0 What is a physical change 0 Changes that alter only the state or appearance but not composition are physical changes 0 The atoms or molecules that compose a substance do not Change their identity during a physical change Exampe When water boils it changes its state from a liquid to a gas 0 The gas remains composed of water molecules so this is a physical change Water molecules change from liquid 0 u 11 physical inr to gas 0 ssta ch 92 Chemical Changes in Matter 0 What is a chemical chanqe 0 Changes that alter the composition of matter are chemical changes 0 During a chemical change atoms rearrange transforming the original substances into different substances 0 Example HA rusting nail is a chemical change 0 Rust occurs when the iron atoms exchange electrons with oxygen atoms combining to form a NEW or different chemical substance 0 Iron rust is the compound iron oxide Fe203 I quot39II lirll il rlli in li39LIili D H I Iiiampi3 ltlasl 1 bl i39i I P 13 s pr 3 391 Writing and Balancing Chemical Reactions Reactions involve chemical changes in matter resulting in new substances Reactions involve rearrangement and exchange of atoms to produce new molecules Reactants gt Products A chemical reaction is a written statement It states the quantities the chemical identity of the substances in the reaction and their physical state Example CH4g 02g gt C02g H20I Chemical Equations Short hand for Describing a Chemical Reaction 0 Chemical equations 0 Provide information about the reaction Molecular or ionic formulas of reactants and products States of reactants and products Gas g liquid I solid 5 and aqueous aq Relative numbers of reactant and product molecules that are required Can be used to determine weights of reactants used and products that can be made The Quantities in Chemical Reactions The amount of every substance used and made in a chemical reaction is related to the amounts of all the other substances in the reaction Law of conservation of mass Balancing equations by balancing atoms 0 The study of the numerical relationship between chemical quantities in a chemical reaction is called stoichiometry Lil14ml 141511ng str lm I 2 Hymn Rectum 7 Pru u tl 39l E Eit l39l i Ii ll xiquot CH3 1 i tnrn l quotl H 72125131 H at u ns u 1 art CH1 EH 4 H alums E HgCl ju 1 E ammsq 2 gr Epl r l Emma l1 97 E x HEB i Reaction Stoichiometry What Is it about 0 The coefficients in a chemical reaction specify the relative amounts in moles of each of the substances involved in the reaction 0 2 C3H18U 25 029 gt 16 C02g 18 H20g What the above BALANCED chemical equation says 0 2 molecules of C8H18 react with 25 molecules of 02 to form 16 molecules of C02 and 18 molecules of H20 0 2 moles of C8H18 react with 25 moles of 02 to form 16 moles of C02 and 18 moles of H20 0 2 mol C8H18 25 mol 02 16 mol C02 18 mol H20 Cooking Stoichiometry Making Pizza 0 The number of pizzas you can make depends on the amount of ingredients you use 0 1 crust 5 oz tomato sauce 2 cups cheese gt 1 pizza 0 This relationship can be expressed mathematically 1 crust 5 oz sauce 2 cups cheese 1 pizza 0 We can compare the amount of pizza that can be made from 10 cups of cheese Since 2 cups cheese 1 pizza then V p V l pizza 6 10 crudscl ie ESe gtlt 5 3122213 2 cupsel39l eese MoletoMole Conversions 2 C3H18I o In the same way that the ratio was used from the pizza recipe example the stoichiometric ratio acts as a conversion factor between the amount in moles of a reactant to moles of a product 0 Reactant to product Stoichiometric ratio 2 moles C8H18 16 moles C02 0 Stoichiometric ratio can be between Reactant to reactant o Stoichiometric ratio 2 moles C8H18 25 moles 02 Product to product Stoichiometric ratio 16 moles C02 18 moles H20 How Many Moles of C02 Form If 220 Moles of CsHls Are combusted Burned Setup and Solution 0 Balanced chemical reaction 2 C8H18 25 029 gt 16 C02g 18 H20g o Stoichiometric ratio from balanced reaction 2 moles C8H18 16 moles C02 0 Calculation 20 lC Hz W W C03 Ht l C i K l mo H h 2 EgHig 39 0 Answer The combustion of 22 moles of C8H18 adds 176 moles of C02 to the atmosphere MoletoMass and MasstoMass Conversions Stoichiometric ratios can be used as a conversion factor between the amount in grams mass of a reactant used to determine mass grams of a product made 0 Strategy A is reactant and B is the product 0 Mass of A gt Moles of A gt Stoichiometric ratio B A gt Moles B gt Mass B 0 mass A x 1 mole Amolmass A x mole Bmole A x molmass B1 mol B 2 C8H18I 25 029 gt 16 C02g 18 H2og 0 Problem 0 Determine the mass grams of C02 produced when 36 x 1015 grams of C8H18 is burned in excess oxygen gas 0 Strategy 0 Need a balanced reaction 0 From the balance reaction use the stoichiometric relationship between C8H18 and C02 0 Mass of C8H18 gt Moles of C8H18 gt Stoichiometric ratio 2 C8H18 16 C02 gt Moles of C02 gt Mass of C02 0 Problem 0 Determine the mass grams of C02 produced when 36 x 1015 grams of C8H18 is burned in excess oxygen gas 0 Strategy 0 Need a balanced reaction 2 C3H18U 25 029 16 C02g 18 H20g 0 From the balance reaction use the stoichiometric relationship between C8H18 and C02 39 2 mol C3H13 mol 02 0 Mass of C8H18 gt Moles of C8H18 gt Stoichiometric ratio 2 C8H18 16 C02 gt Moles of C02 gt Mass of C02 0 36 x 1015 grams C8H18 x 1 mol C8H1811422 g x 2 mol C8H1816 mol C02 x 440 g1mol C02 11 x 1016 grams of C02 is produced Limiting Reactant Theoretical Yield 0 Back to the pizza recipe 0 1 crust 5 oz tomato sauce 2 cups cheese gt 1 pizza 0 Suppose you have 4 crusts 10 cups of cheese and 15 oz tomato sauce How many pizzas can you make Strategy 4 7 X l pizza 4 crusts Jams 0 We have enough crusts to make 1 crtrs39t p 7 l pizza ill cupscheese gtlt Z plZE S 0 We have enough cheese to make 2 LUPh39fli e 0 We have enough tomato sauce to make 15 X 7 1 pizza 2 3 pizzas Limiting reactant Smallest number of pizzas We have enough crusts for 4 pizzas enough cheese for 5 pizzas but ONLY enough tomato sauce for 3 pizzas Therefore only 3 pizzas can be made The tomato sauce limits how many pizzas can be made 4 crusts 4 pizan f if i r if if i l 3 i 10 mpg cheese 5 l5 ounces wizms le39ltlng mm msauce Least amount 3 p T Theoretical reactant of product yield Limiting Reactant and Theoretical Yield Connection In the pizza analogy the tomato sauce is the limiting reactant the reactant that ma kes the least amount of product The limiting reactant is also known as the limiting reagent The maximum number of pizzas that can be made depends on this ingredient the tomato sauce ln chemical reactions this is called the theoretical yield Theoretical yield is the amount of product that can be made in a chemical reaction based on the amount of limiting reactant Example The ingredient that makes the least amount of pizza determines how many pizzas you can make theoretical yield More Making Pizzas Assume that while making pizzas a pizza is burnt or dropped on the oor and only two pizzas are available to eat The actual amount of product made in a chemical reaction is called the actual yield Actual yield is about efficiency To determine your efficiency in making pizzas a percentage value can be calculated ln chemical reactions this is called a percent yield Actual yield 2 gpirgifas mg will 7 gtlt iliiiii my HimFm Theoretical yield Summarizing Limiting Reactant and Theoretical Yield The limiting reactant or limiting reagent is the reactant that is completely consumed in a chemical reaction and limits the amount of product The reactant in excess is any reactant that occurs in a quantity greater than is required to completely react with the limiting reactant The theoretical yield is the amount of product that can be made in a chemical reaction based on the amount of limiting reactant The actual yield is the amount of product actually produced by a chemical reaction The percent yield is calculated as actual yield theoretical yield x 100 percent yield Chemical Reaction 0 In reactions with multiple reactants it is likely that one of the reactants will be completely used before the others 0 When this reactant is used up the reaction stops and no more product is made 0 The reactant that limits the amount of product is called the limiting reactant o It is sometimes called the limiting reagent 0 The limiting reactant gets completely consumed Reactants not completely consumed are called excess reactants o The reactant in excess is any reactant that occurs in a quantity greater than is required to completely react with the limiting reactant o The amount of product that can be made from the limiting reactant is called the theoretical yield Combustion A Type of Chemical Reaction A combustion reaction involves the reaction of a substance with 02 to form one or more oxygen containing compounds Other products of a combustion reaction WaterH20 and Heatenergy 0 Example Combustion of methane o CH49 2 029 gt C02g 2 H20g Heat Alkali Metal Reaction A Type of Chemical Reaction 0 Overview of Alkali Metals o The alkali metals group 1A have n51 outer electron con gurations Form 1 cation to achieve noble gas con guration 0 The reactions of the alkali metals with nonmetals are vigorous 0 Common reaction for alkali metals M is with halogens X 39 2 M X2 2 MX Example 2 Nas C2g gt 2 NaCls o The alkali metals react vigorously with water to form the dissolved alkali metal ion the hydroxide ion and hydrogen gas 2 Ms 2 H20l gt 2 Maq 2 OH39aq H2g The reaction is highly exothermic and can be explosive because the heat from the reaction can ignite the hydrogen gas Reactions the Alkali Metals with Water Halogen Reaction A Type of Chemical Reaction Haloden Overview 0 Group 7 elements that have nsznp5 outer electron con gurations Mostly form 1 anions F only forms 1 anion to achieve the quotnoble gas con gurationquot Most reactive of the nonmetal elements 0 The halogens X tend to react with metals especially with Group 1 and 2A metals to form ionic compounds such as metal halides MXn 2MnX2 gt2MX7 Example 2 Fes 3 C2g gt 2 FeCI3s o The halogens react with hydrogen to form hydrogen halides 39 H2 9 X2 2 HX9