CHM 103 1st Edition Exam 2 Study Guide Chapters 4 and 7 Chapter4 4 2 Reaction Stoichiometry How Much Carbon Dioxide o 2 C8H18 l 25 O2 g 16 CO2 g 18 H2O g o The balanced chemical equation provides the ratios of the substances involved Law of conservation of mass Balancing equations by balancing atoms o The study of the numerical relationship between chemical quantities in a chemical reaction is called stoichiometry o The coefficients in front of the molecules represent the ratio that they react in Ex In the above reaction 25 moles of oxygen are required to completely react with 2 moles of C8H18 4 3 Limiting Reactant Theoretical Yield and Percent Yield o Limiting reactant the reactant that is consumed first and therefore limits the amounts of products that can be formed o Theoretical yield the amount of product that can be made in a chemical reaction based on the amount of limiting reactant o Problem If Alice drank 350 mL of 1 2M magnesium chloride from the first pool and 250 mL of 1 5M silver nitrate from the second pool what is the maximum precipitate that can be produced Upon necropsy only 35 0g of the AgCl precipitate was recovered What is the percent yield Assume all of the solutions are aqueous Given 350 mL of 1 2M magnesium chloride from first pool 250 mL of 1 5M silver nitrate from the second pool 35 0g of precipitate was recovered Unknown Maximum amount of AgCl formed percent yield 2AgNO3 aq MgCl2 aq 2AgCl s Mg NO3 2 aq 250 L AgNO3 350 L MgCl2 1 5 mol AgNO3 2 mol AgCl 143 32 g AgCl L 2 mol AgNO3 1 mol AgCl 1 2 mol MgCl2 2 mol AgCl 143 32 g AgCl L 1 mol MgCl2 1 mol AgCl 54 g AgCl 120 g AgCl Which reactant yields the least amount of product That is the limiting reactant In this case AgNO3 is the limiting reactant with a maximum yield of 54 g AgCl Percent yield Actual yield Theoretical Yield 4 4 Solution Concentration and Solution Stoichiometry o Solute gets dissolved o Solvent does the dissolving larger quantity o Dilute solutions have a small amount of solute compared to solvent o Concentrated solutions have a large amount of solute compared to solvent o Concentration density Precipitation reactions double displacement o Predict the products o Complete ionic and net ionic equations don t break up solids Acid Base reactions double displacement o Predict the products o Complete ionic and net ionic equations don t break up water o Titrations specific case of solution stoichiometry Gas Evolution GE reactions double displacement o Predict the products memorize the 4 GE products H2S is a gas H2SO3 aq H2O l SO2 g H2CO3 aq H2O l CO2 g NH4OH aq H2O l NH3 g o Complete ionic and net ionic equations don t break up gases Oxidation Reduction Reactions single displacement o Loss of electrons oxidation gain of electrons reduction o Be able to calculate oxidation numbers o Predict the products using the Activity Series o Complete ionic and net ionic equations know the difference between a metal in the solid state and a metal ion in aqueous solution Chapter 7 The wave particle nature of electromagnetic radiation light o A wavelength is from one point in the wave to another identical point ex crest to crest or trough to trough o Speed of light 3 00x10 8 m s c The amplitude is the distance from the height of the crest to the trough Frequency is the number of crests and troughs over a certain amount of time shown as 1 s or Hz o Wave properties light has a wavelength and a frequency speed of light 2 998 108 m s in a vacuum c memorize the COLOR of light depends on its wavelength or frequency o Particle properties Photoelectric effect light travels in bundles known as quanta or photons energy of 1 photon E h h Planck s constant memorize energy of n photons E nh Electromagnetic spectrum o Radio Microwave Infared Visible light Ultraviolet X Ray Gamma These are in lowest to highest wavelength energy order o Pneumonic Red Martians invade Venus using x ray guns Interference o Constructive In phase the crests and troughs of the wave match up and create a larger amplitude o Destructive Out of phase the waves to not match up and the two waves end up cancelling each other out Photoelectric effect o Many metals give off an electron when a light is on it it s what makes them shiny o Inversely proportional to its o This uses Planck s constant Atomic Spectroscopy and the Bohr Model of the atom o Emission spectra of elements line spectra not continuous o Bohr model solar system model electrons move to a lower orbit lower n photon is released E is negative emits light electrons move to a higher orbit higher n photon is absorbed E is positive does not emit light En 2 18 10 18J 1 n 2 Eelectron Ephoton the energy released absorbed by the movement of the electron is equal to the energy of the photon emitted absorbed The wave nature of matter o The de Broglie equation h mv h Planck s constant m mass of particle in kg v speed of particle in m s o Be sure to use o The Heisenberg Uncertainty Principle you cannot know the position and the momentum speed of a particle exactly