Notes from Week of 10/5
Notes from Week of 10/5 CHEM-1070-40
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This 4 page Class Notes was uploaded by Dkrefft on Monday October 12, 2015. The Class Notes belongs to CHEM-1070-40 at Tulane University taught by Lopreore, Courtney in Fall 2015. Since its upload, it has received 49 views. For similar materials see General Chemistry I in Chemistry at Tulane University.
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Date Created: 10/12/15
Chapter 6 Gases 105 Pressureforce per unit area FN o 1 atm 760 torr 760mm Hg 101325 kPa General gas equation where p pressure v volume n number of mols t temp Constant temperature for a fixed amount Pi Vi Pfo E Boyle s law PiVi Pfo where pressure is inversely proportional to volume Charles s law volume is directly proportional to temperature at constant pressure Always use K 27315 C K Vi Vf T7 E Standard temperature and pressure STP 0 deg C and 1 atm 1 mole of gas 22414 L ldeal gas equation R 00821 atmLmolR 1 atm x 22414L quoti Ti o R 1 mglex 27315K 0 PV mM m mass and M molar mass MP o d g E the lower the molar mass the greater the lifting power Gases in chemical reactions Law of combining volumes 0 Consider 2N0g 02 g gt 2N02 g the 2 represents the two moles o 2 mols of NO g 1 mol 02 g 2 mols N02 9 o If gases are compared at the same temperature and pressure we can substitute the mols for volumes so 0 2L N0g 1L 02g gt 2L N02g What volume of N2g measured at 735mm Hg and 26 degrees C is produced when 750g NaN3 is decomposed o 2NaN3s gt 2Nal 2N2g 0 find mols first so 750g NaN3 x 1m0 NaN3 3m0 N2 173 molNz 6501g NaN3 2 mol NaN3 assume ideal gas behavior P 735mm Hg x i 0967 atm 760 mm Hg 173 l 00821Latm 299K 0 VnRT max mom 439L P 0967atm Mixtures of gases 2 equations 2 unknowns The total pressure of the mixture is determined by the total number of mols ntotRT 0 PM at constant 17 and t o Vtot at constant p and t Dalton s Law of Partial Pressures 0 PW PaPb 0 each expands to fill its container and exerts the same pressure as if it were alone 0 In a mixture of n moles of A nb moles of b and so on 1v RT NbRT I V a V a Ptot b Ptot total volume is additive vtot Va Vb V volume A a x 100 N p a O a a a xa Ntot Ptot Vtot o xa xb 1 all components in mixture add to one Collecting a gas over liquid o 2Al S 6HCl aq gt 2AlCl3aq 3H2 g o If 355 mL of H2 g is collected over water at 26 degrees Celsius and 7492 mm Hg how many moles of HC are consumed Vapor pressure of H20 at 26 C 252 mm Hg 0 PM PHzo PHZ 7492 252 7744 mm Hg 1019 atm 0 V 00355 L 1019atm00355L 3 O Ntot 0032226th29915 L473 0 NA2 ntotNH2 1422e 3mol tot o 1422e 3 molH2 x M 284e 3 mol HCl consumed 3 mol H2 Non ideal gas You can account for intramolecular forces of attraction Van der Wal s equation 2 o P v nb nRt a and b vary from molecule to molecule pter 7 Thermochemistry Cha system the part of the universe chosen for study usually small surroundings outside of the system with which the system interacts open system can freely exchange energy and matter with surroundings closed system can exchange energy but not matter isolated system doesn t interact with the system at all No energy no matter Energy the capacity to do work Work is done with a force acts through a distance Kinetic energy energy of a moving object 1 o ek Emu2u veloczty o w mad 1kgm2 32 potential energy stored energy with potential to work thermal kinetic energy associated with random molecular motion Directly proportional to temperature of a system oc N of particles more energy More particles heat energy transferred bw a system and surroundings as a result of change in temperature heat will transfer until the kinetic energy of both are the same The change of temp can change the state of matter q heat depends on quantity and nature substance Calorie heat required to change temp of one gram of degrees C 1 cal 4184J Heat capacity quantity of heat required to raise the temp of one degree Celsius 0 energy gt joule 0 If system is mole it s a molar heat capacity 0 If a system is one gram it s a specific heat capacity 0 At 25 degree specific heat of water 418 Jg deg C 0 Not referring to specific heat No grams in denominator Q m x specific heat x change in temp 0 Heat capacity m x specific heat change in temp tfinal t initial 0 If q is positive heat is absorbed or gained negative heat is evolved or lost Q system q surround 0 Q system q surround Calorimetry O O O 0000 O 0 109 Heats of reaction and calorimetry Chemical energy Q reaction heat of reaction quantity of heat exchanged between a system and surroundings at a constant temp Exothermic produces temperature increase in an isolated system or gives heat to surroundings in nonisolated systems q reaction lt 0 so negative Endothermic temperature decreases in an isolated system or gains heat from surroundings in non isolated system q reaction gt 0 so positive Bomb calorimeter measures heat in a combustion reactions all the surroundings the calorimeter Q reaction q calorimeter q calorimeter q bomb q H20 q thermometer The combustion is the system 0010g C12H22011 Ti 2492 C Tf 2833 C heat capacity of calorimeter 490 kJC q caor 49211 2833 2492 167 K 3 CI TeactiOTl q calorimeter w m 539653 k1 1010g mol mol 0 coffee cup calorimeter O 0 mix reactants generally aqueous in a Styrofoam cup and measure temperature change the cup contents isolated system 0 heat of reaction quantity of heat that would be exchanged with surroundings in restoring calorimeter to its initial temperature 0 q reaction q calor H aq OH 9 H2O liquid 0 00000 0000 Two solutions added to Styrofoam cup 250 mL of 250 M HCI 250 mL of 250 M NaOH tinitial211 C tfinal 378 C determine reaction per mol of H20 formed Density of H20100 gmL specifc heat capacity of water 418 Jg C q calor 50mL x1gmL x 418Jg C 378211 C 350e3j q reaction q calor 35 kj is evolved released 25 molL 0025L 00625 mol q rxn 35 kJ 00625 mol H2O formed 56 kJmol exothermic reaction 0000000000 0 pressure volume work the work involved in the expansion or compression of a gas Pathwork w force x distance 2KI03 s 9 2KCIs 302 9 pressure forcearea work m x ga x change of height x a Pext AV AV gt 0 wlt 0 energy leaves as work expansion AVltO wgt0 energy enters compression 1 bar L 100J 1 L atm101325J Determine W 0225 mol N2 at constant t23 C is allowed to expand by 150L in volume against an external pressure 0750atm W PextAV 0750atm150L101325Jmol 114e2 J of work done by the system