Midterm 3 Study Guide
Midterm 3 Study Guide CHMY 141N - 00
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This 4 page Study Guide was uploaded by Isabella Sturgeon on Monday November 2, 2015. The Study Guide belongs to CHMY 141N - 00 at University of Montana taught by Mark Cracolice (P) in Fall 2015. Since its upload, it has received 35 views. For similar materials see College Chemistry I in Chemistry at University of Montana.
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Date Created: 11/02/15
Chemistry 141 Lesson 18 How are Measureable Gas Quantities Related in a Chemical Change when One or More Species is a Gas This lesson demonstrates how to use the density of a gas and what the significance of the density is Essentially you will use stoichiometry and gas laws to solve any problems that uses gasses and other phases Density m This is a modification of the ideal gas law PVN RT It can be rewritten using algebra to solve for mass over volume which is density DmMMP 12 RT This is the molar mass times pressure over the gas constant times temperature Molar Volume Is the amount of volume per mole of gas MV V RT n P This is found by the gas constant time the temperature divided by pressure Lesson 20 How is Energy Related to Chemical Systems and Chemical Change This lesson is essentially all about energy Once again stoichiometry will be used only this time the amount of heat in the balanced chemical equation can be used as a conversion factor There are also a couple new conversions to keep in mind calorie to Calorie and calorie to joule Conversions 1000 calories 1 Calorie 4184 Joules 1 calorie Understand the concept of work I like to think of it as the amount of work being done on an object Exothermic releases heat into the surroundings so it will feel hot this have a negative enthalpy when regarding the system Endothermic takes in heat from the surroundings so it feels cold and has a positive enthalpy The first law of thermodynamics is AE q w State function a number that can be solved by simply subtracting the end fro the start Think about numerical values that make sense to solve this way Ex Change in elevation versus distance traveled The change in elevation would be the state function because it can be figured out in one simple math problem When the Enthalpy AH is positive the reaction is endothermic because there is heat being taken into the system Think about ice melting it requires energy When Enthalpy AH is negative the reaction is exothermic because there is heat being released into the surrounding ce freezing releases energy into the surroundings because it is cooling off Lesson 21 What are the Relationships Among Heat Energy Temperature and Mass for Pure Substances This less focuses on the relationship between heat and mass The amount of heat needed to melt a substance is directly proportional to its mass This leads to the knowledge of heat of fusion and vaporization which are essentially the energy required for a phase change of a certain substance However that is not all There is still energy that can be gained during one phase as the temperature increases This lesson demonstrates the equation for this Heat of Fusion melting Heat of Vaporization same equation but the constant will be AHvap q AHqu E This equation can be algebraically rearranged to solve for any of the three parts Make sure to pay attention to units Heat of vaporization usually is expressed in KJg while heat of fusion is usually Jg When energy changes but phase does not This is derived from the directly proportional relationship of energy transfer to mass and the change in temperature q chT The constant c is used to turn the proportionality stated above into an equation It is the specific heat of the substance Make sure to pay attention to the substances boiling and melting points because you will need to switch between the two equations depending on the temperature and where a phase change occurs Lesson 22 How are Heat Energy Changes Determined This lesson introduces the calorimeter which is used to determine the specific heat of an object or the heat flow for a reaction Most are imperfect requiring calculations to determine the amount of heat the calorimeter takes in from the reaction This constant can be solved by a series of calculations In this lesson also shows how to find the heat content of an element or compound Calorimetry Can be used to find the specific heat or total energy flow For specific heat find the energy of the liquid in the calorimeter and put that into the equation q chT Using algebra solve for c For heat flow find the q of the hot water q of the cold water which can find the q of the cup All add to zero theoretically When the q of the cup is found the Kcal can be solved for knowing that is is equal to the q of the cup over the total temperature change Temperature change always is final minus initial Heat of Formation Can be found in the data pack for each compound To find the standard state of enthalpy change for a reaction use this equation AHO 201 AHfproducts 2n AHfreactants After this is calculated it can be turned into a stoichiometry equivalency Hess s Law To do a Hess s Law problem you need to take multiple equations and add them together until they equal the original equation This may involve flipping doubling or halving Lesson 23 How are Electrons Distributed Within an Atom Bohr Model This lesson introduces the concept of quantum mechanics and the electromagnetic spectrum This leads to the introduction of waves and how to calculate the velocity from speed and wavelength Low temperature is low light intensity radiated and so on Light packet is called a photon Waveparticle duality behaves like both a wave and particle travels like a wave arrives like a particle This lead to the hypothesis that electrons have specific orbits and are never in between because of quantum jumps Energy of a hydrogen atoms jumping between two quantum levels is calculated from the following equation 1 1 AB RH E nal RH Emmal Make sure to always do final initial Lesson 24 How are Electrons Distributed Within an Atom The Quantum Mechanical Model This lesson is all about calculating wavelength for a moving particle The Heisenberg Uncertainty Principle is also introduced which is the idea that you can either know the position or velocity but not certainly both Quantum Mechanical Model n is the quantum number or principal energy level I is n1 which is the quantized sublevel this is where the spdf come from ml is the orbital quantum number which ranges from to Remember that each identified sublevel will have a number of orbitals To figure out the number of electrons take the spin options and multiple by the number or orbital options Lesson 25 How are Electrons Distributed Among Orbitals Within an Atom This lesson brings the periodic table arrangement into energy sublevels It also introduces the two principles of writing electron configuration This also leads to the electron configuration and a deeper understanding of writing this and noble gas configuration Valance electrons are the outermost electrons that have the ability to make bonds These can be shown through a Lewis Dot Structure
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