Chem 111 Week 7 lecture notes
Chem 111 Week 7 lecture notes 111/40551
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This 8 page Class Notes was uploaded by firstname.lastname@example.org Notetaker on Wednesday October 21, 2015. The Class Notes belongs to 111/40551 at University of St. Thomas taught by Uzcategui-White in Summer 2015. Since its upload, it has received 11 views.
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Date Created: 10/21/15
CHEMISTRY WEEK 7 LECTURE NOTES Chapter 5 continued 0 Kinetic Molecular Theory 4 Collection of particles in constant motion No attractions or repulsions between particle collisions like billiard ball collisions A lot of space between the particles compared to the size of particles themselves The speed that the particles move increases with increasing temperature 0 Ideal Gases Are compressible Assume the shape and volume of the container Have low density values Ek 12 mass x speed quot2 Heavier gases move slower o Effusion the process by which a gas escapes through a small hole in the container into an evacuated space Graham s law of effusion the rate of effusion of a gas is inversely proportional to the square root of its molar mass Speed 1 square root of its molar mass Two gases U rms root mean speed Rate A Rate B Square root of Molar mass b molar mass a o Diffusion movement of one gas through another Molecules are in constant motion and tend to move from regions Problem 556 What is the ratio of effusion for 02 and Kr U Square root of 8380 g mol 32 g mol 168 0 Real Gases The kinetic molecular model describes the behabior of ideal gases Real gases have real volume Gas particles are not points of mass but have volumes determined by the sizes of their atoms and bonds between them Real gases experience attractive and repulsive forces between their particles Real gases deviate from ideal gas behavior at low temperature and high pressure Van der Waal P nquot2a v v nb nRT a relates to factors that influence the attraction b relates to particle volume Chapter 6 Thermochemistry o Thermodynamic the study of energy and its transformations 0 Thermochemistry a branch of thermodynamics that deals with the heat involved in a chemical or physical change transfer of energy 0 System defined as an object or collection of objects being studied Surroundings includes everything outside the system that can exchange energy an dor matter with the system System surroundings universe Internal energy E or U sum of potential energy and the kinetic energy of all the particles present Change in E E final E initial E reactant E reactants a By releasing energy in a transfer to the surroundings E final lt E initial change in E lt 0 b By absorbing energy in a transfer from the surroundings E final gt E initial change in E gt0 Heat and Work two forms of energy transfer 1 Heat or thermal energy q 2 Work w Heat Transfer of heat is spontaneous Highter T to a lower T value Result of temperature difference between system and surroundings Until both has the same temperature Ex cold drink in the summer Surrounding gives energy to drink Work Energy transferred when the object is moved by force When work is done in an object results in change of object s kinetic energy Ex kicking a football 0 The total change in a system s internal energy is the sum of the energy transferred as heat and or work 0 Change in Eqw 0 Only q energy transferred only as heat Change in E q W 0 a Heat flowing out from the system Q lt 0 9 change in E lt 0 negative Heat is released from the system b Heat flowing into the system Q gt 0 9 change in E gt 0 positive Heat is absorbed from the surrounding 0 Only w energy transferred only as work Change in E w q 0 a Work done by the system W lt 0 change in E lt0 b Work done on the system W gt 0 change in E gt 0 Law of Energy conservation first law of thermodynamics 0 quotenergy is conserved the total energy of the system plus the surrounding remains consta nt 0 energy in the universe energy of the system energy of the surroundings 0 E does not depend on how the changes take place but only the difference between the final and initial states State of function 9 initial and final Units of Energy 0 SI 9 Joule J 1 1 k x mquot2squot2 1 kJ 1000 o Calorie cal 9 energy transferred to raise the temperature of 100 g of water by 1 degree C 1 cal 4184 1 kcal 1000 cal o The dietary calorie 9 food 1 Cal 1kCal 1000 cal Problem 61 If you feel warm after exercising have you increased the internal energy of your body No the internal energy decreases because the heat decreases as well as the work 66 A system releases 255 cal of heat to the surroundings and delivers 428 cal of work What is the change in the internal energy of the system Q 255 cal W 428 cal E q w 9 E 255 428 683 cal 68 Thermal decomposition of 50 metric tons of limestone to lime and carbon dioxide absorbs 90 x 10 quot6 k of heat Convert the energy to calories 90 x 10quot6 k x 1000 J 1 k x 1 cal 4184 22 x 10 quot9 Enthalpy o the transferring of energy as heat at constant P 0 chemical change at constant P for reactions at constant P a thermodynamic variable called enthalpy H H E PV Change in H q Change in H q qp heat released absorbed at constant P a exothermic change 9 releasing energy heat reactants 9 products heat H lt 0 Ex CaC2 s 9 Ca 2 aq 2Cl aq heat b endothermic change 9 absorbing heat reactants heat 9 products Hgt 0 Ex NH4N03 s heat 9 NH4 aq N03 aq Calorimetry o the heat of a chemical physical change 0 use calorimeter to make sure amount of heat transferred 0 Heat Capacity q T heat change in Temperature Joules Kelvin 0 Specific Heat Capacity c Takes into consideration mass of object Quantity of heat required to change temperature of 100 g of water or object by 1 K C q mass of object x T q c x mass x T 625 A 277 g sample of ethylene glycol releases 688 J of heat What was the initial temperature of the sample if the final temperature 325 C c of ethylene glycol 242 J g K M 277 g Q 688J Ti Tf 325 C 9 3055 K C 242 Jg k q c x mass x temperature T 688 J 242 J g k x 277 g 103 K T initial T final 103 T initial 3055 k 103 K 316 K 428 C