GENERAL CHEMISTRY CH 121
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This 17 page Class Notes was uploaded by Dariana Wolff on Monday October 19, 2015. The Class Notes belongs to CH 121 at Oregon State University taught by R. Nafshun in Fall. Since its upload, it has received 57 views. For similar materials see /class/224552/ch-121-oregon-state-university in Chemistry at Oregon State University.
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Date Created: 10/19/15
Chemistry 121 S Worksheet 1 Notes Summer 2006 Oregon State University Dr Richard Nafshun 13 2 For each system below give the signs positive or negative for w q and E A B C D E Energy W work 1 heat A system does 10 k of work and gives off 220 k of heat E 220 kJ 10 kJ 230 k The heat 220 1d is negative because the system is giving off heat exothermic The system now has 220 1d less energy than it had before The work 10 kJ is negative because the system did work it no longer has the ability to do that workiit give it away E is calculated to be negative although a calculation was not needediboth the heat and work were negative leading to E being negative A system does 50 k of work and absorbs 65 1d of heat E 65 1d 50 1d 15 k The heat 65 1d is positive because the system is received heat endothermic The system now has 65 kJ more energy than it had before The work 50 1d is negative because the system did work it no longer has the ability to do that workiit give it away E is calculated to be positive the system gained energy overall because it gained a greater amount of heat than the work it output A system does 10 k of work and gives off 220 k of heat Accidentally the same question as Part A A system has 120 k of work done on it and gives off 50 1d of heat E 50 1d 120 kJ 70 k The heat 50 1d is negative because the system is giving off heat exothermic The system now has 50 kJ less energy than it had before The work 120 kJ is positive because the system received work it now has the ability to do that workiit received work and can give it away later E F G H E is calculated to be positive the system gained energy A system has 70 1d of work and gives off 85 1d of heat Itook this question to mean that the system has 70 k of work done on it it should be worded a bit clearer E 85 1d 70 1d 15 k The heat 85 kJ is negative because the system is giving off heat exothermic The work 70 kJ is positive because the system received work it now has the ability to do that workiit received work and can give it away later E is calculated to be negative the system lost energy A system does 75 k of work and gives off 75 k of heat E 75 1d 75 kJ 150 k A system cools down while expanding E t q is negative because the system cools downiit gives off energy to become cooler w is negative because the system expands does work A system heats up a little while expanding a lot E t t q is positive because the system heats upiit receives energy to become hotter Endothermic w is negative because the system expands does work E is negative because the is small and the is large I 14 4 A endothermic reaction does not expand E 0 q is positive because the system heats upiit receives energy to become hotter Endothermic w is zero no work is doneieither on the system or by the system E is positive because q is and w 0 The heat offormation ofurea CONH22 s is 733319 kJmol Write the chemical equation associated with this reaction include phasesis l g or aq C graphite 2 Hz g 12 02 g N2 g gt CONH22 s AHof 733319 kJ Table 62 will be helpful How much energy is given off when 800 moles of CO g is formed from the elements at 25 C and 1 atm C graphite 12 02 g gt co g AHOf 71105 k 1105 k of energy is given offwhen one mole of CO g is formed So when 8 moles of CO g is formed 1105kJ 800 moles CO 1mole CO J 8840 k 8840 k of heat energy is given off when 8 moles of CO is formed How much energy is given off when 5000 g CO g is formed from the elements at 25 C and 1 atm 5000 g CO M 1785 moles CO g 28 01g 1785 moles CO 1973 1d 1mole CO 1973 k of heat energy is given off when 5000 g of CO is formed Consider 2 C8H18 l 25 02 g gt 16 C02 g 18 H20 1 AHZWHOH 10900 kJ How much energy is released when one mole of octane Cngg is combusted 10900 1d of heat energy is released when two moles of octane are combusted this is what the balanced equation says When one mole of octane is combusted 1 mole w 5450 k 2 moles CBH18 l 5450 k of heat energy are released What is AH when 9 moles of water are formed 10900J 9 moles H20 1 18 moles H20 1 J 5450 k Table 62 will be helpful Calculate AH for the following reaction CH4 g 2 02 g gt C02 g 2 H20 1 AHZWHOH CH4 g 2 02 g gt C02 g 2 H20 1 AHof 7485 kJmol 0 kJmol 3935 kJmol 2859 kJmol AHureaction Z AHuproducts 39 Z AHureactants AH reaction lmol com 3935 ldmol 2 mol H2O2859 kJmol 7 1 mol CH47485 kJmol 2 mol 020 kJmol AH reaction 9653 Id 7 7485 kJ 89045 kJ Exothermicienergy is released of course it is This is the combustion of methaneinatural gas We do this reaction to cook and heat our liVing spaces Table 62 will be helpful Calculate AH for the following reaction C2H2 52 02 gt 2 C02 H20 AHereaction C2H2 g 52 02 g gt 2 C02 g H20 1 AHof 22675 kJmol 0 kJmol 3935 kJmol 2859 kJmol AHureaction Z AHuproducts 39 Z AHereactants AHZeamon 2 mol C023935 kJmol 1 mol H202859 ldmol 7 1 mol C2Ho 22s 75 kJmol 52 mol 020 klmom AH mccm 71300 kl hermxcienergy is released ofcourse tttst This is the eombustmh of another hydrocarbon this one is acetyleneiusedm torches We do this reaction to weld and eut holes m meta1 The heat efformauon ofN39HoCl s is 7315 4 kJmol whte the ehemtea1 equatmh assomated Wth this heaetmh melude phasesis 1 g or aq 2N2g2H2C12ggtN39HoCls AH 4154a From the followmg heats ofreacuon 2502g02g 250M AH 1 25s302g gt2503g 2 ea1eu1ate the heat ofreacuon for 5s 02g gt 502g AH 71d 3 thped equatmh 1 and dwxdedxtby 2 we dmded equation 2 by 2 AH 7297 km 3 Calculate the standardreacnon ehtha1py for the photosynthesxs reaction 6lt3023 6H20I c6H12065 6025 A8 714 H text AH MW 2 AHquot products 7 2 AH reactacnts AH Mm 1 mol c Hzo s71274 5 kJmol 6 mol 0 g0 kJmol e 6 mol cozge393 5 kJmol 6 mol H201e285 8 kJmol 12 16 1 Given the following reactions and their enthalpy changes calculate the enthalpy change for 2 Noug gt N204g Equations Change in Heat Energy Nzcg 2 022 gt 2 N02 678 k Nzcg 2 022 gt N204g 967 k Leave the bottom reaction and ip the first N2ltggt t 2 02ltggt gt N204ltggt 2 Nozcg gt Nzg 2 02g The nitrogen and oxygen cancel leaving 2 Nozg gt N204g macawquot 678 kJ 967 1d 58 13 kJ What is meant by quotquantaquot Packets of energy Sketch the entire electromagnetic EM spectrum with the highest energy on the left Label each region gamma Xray ultraviolet UV visible etc Label the highest and lowest energy regions Label the highest and lowest frequency regions Label the longest and shortest wavelength regions Does it make sense that UV is to the left of visible Explain Which has a longer wavelength blue or red light Which has a higher frequency blue or red light Which has a higher energy blue or red light Dmnnf mm ml w l m w m A l m lava W l mm m ngh Energy Low Energy ngh Frequency Low Frequency snon Wavelength Long Wavelength rm Fr all u wd has alongerwayelenglln What ls meant by ROY GBIV7 Red Orange Yellow Green Blue Indlgo Vlolet Why is there a demand for blue lasers What color is the laser in a CD player Which one a blue or a red laser has a shorter wavelength Which one a blue or a red laser has a greater energy The current lasers in CD players are red or IR Blue lasers are higher in energy and shorter wavelength Blue lasers enable more data access a CD will hold more information than today39s CDs What is the color of light that has a wavelength of 532 nm What is the frequency of this light What is the energy of one photon of this frequency What is the energy of one mole of photons of this frequency 532 nm looks to be in the green visible region v cx 300 x108 mS532 x10399 m 564 x1014 Us or Hz E hv 6626 x 103934 Js564 x1014 ls 374 x 1039 J per photon Note When an electron quotfallsquot from one energy level to another electromagnetic radiation is emitted One electron quotfallingquot corresponds to one photon 602x1023 photons 374 x 1039 Jphoton lmole J 224935 Jmol or 225 ldmol What is meant by the ultraviolet radiation regions UVA 315400 nm UVB 290315 nm and UVC 100290 nm Which is most dangerous Why UVC has the shortest wavelength it is the most dangerous because it is the highest in energy UVA has the longer wavelength of the three it sits nearest violet light What is the wavelength in nanometers of light that has an energy content of 508 kJmol photons In what portion of the electromagnetic spectrum will this light be found What portion of the electromagnetic spectrum lies to the right Is this portion higher or lower in energy E hck this energy corresponds to the energy of one photon the energy given in this problem is for one mole of photons so we will change this after we change the units from k to J 508 kJmol photons M101 phomm f 844 x 1039 Jphoton lkJ 602x10 photons E hck Rearranged 7t hcE 6626x10 34J o s300x108 a x 195 236X10399mor236nm 844X1039 J From the EM gure above this appears to be in the UV region Question 6 above con rms this and pinpoints this emission in the UVC region The region that lies to the right of UV is visible it is lower in energy than UV What is the wavelength in meters of the FM signal broadcast from KBVR radio at a frequency of 887 MHz 887 X 106 Hz Is this long or short compared to the wavelength of the color you determined in Question 5 vc7t Rearranged 7t cv 300 X 10398 ms887 X 106 US 338 m Much longer wavelength than visible light CONCEPT ON FINAL EXAM BUT THE CALCULATION IS NOT ON FINAL EXAMX Given that the energy level for the n 1 level in the hydrogen spectrum is l312 kJmol calculate the energy for the n 2 n 3 n 4 n 5 and n 00 levels 431231 7 m0 E7 2 1 Recall E 1s proportlonal to 7 n n Emgy kJmnl Energy Levels in Baku HrAtnm n g Em mm 1 mm 2 2mm 3 14572 4 mm 5 5242 5 2544 7 2m 2 2mm 9 7mm m 71312 4312i 172W 71312kJmol 4312i 7 7328 kJmol Id kJ 43127 43127 E3 2 01 2 01 146kJmol n 3 43127 43123 E4 Zmo 2m01 821dmol n 4 43123 43123 E5 2 01 2 01 521dmol n 5 43123 43123 E00 2 0 2 01 OkJmol 7 00 Do these values match those in the table above They should Which hydrogen atom has absorbed more energy one in which the electron moved from the rst to the third energy levels or one in which the electron moved from the second to the fourth energy levels Explain First to the third energy level Look at the energy diagram above The gap between n l and n 3 is huge compared to n 2 to n 4 The energy relationship is CONCEPT ON FINAL EXAM BUT THE CALCULATION IS NOT ON FINAL EXAMX 1312 mol quot2 so the energy is proportional to lnz In the hydrogen atom how much energy is required to remove one mole of electrons from the n 1 energy level How much energy is required to remove one mole of electrons from the n 5 energy level How much energy is required to excite one mole of electrons from n 1 to n 3 CONCEPT ON FINAL EXAM BUT THE CALCULATION IS NOT ON FINAL EXAMX 1312 1312 E1 2mol l Zmol 1312kJmol 7 so it takes 1312 k to remove one mole of electrons from the n 1 energy level 1312 43123 E5 mo 52 quot101 521dmol 2 7 so it takes 52 1d to remove one mole of electrons from the n 5 energy level The energy required to excite one mole of electrons from n 1 to n 3 is E3 7E1 43123 43123 01 01 11661dmol 32 12 so it takes 1166 k to excite one mole of electrons from n 1 to n 3 How much energy is released from one mole of electrons when they relax from n 3 to n 2 What is the wavelength and color ofthis emission CONCEPT ON FINAL EXAM BUT THE CALCULATION IS NOT ON FINAL EXAMX E27133 1312 1312 22mol 3 2739101 182kJmol so 182 1d of energy is released when one mole of electrons quotfallsquot from n 3 to n 2 THIS CALCULATION IS GOOD TO KNOW FOR THE FINAL EXAM E hck this energy corresponds to the energy of one photon the energy calculated in this problem is for one mole of photons so we will change this after we change the units from k to J 302 x 1039 Jphoton 182 kJmol photons IOOOJ mi lkJ K602x1023 photons E hck Rearranged 7t hcE 6626x10 34J o s300x108 a x 5 657X10399mor657nm 302x103919J From the EM gure above this appears to be in the red region of the Visible spectrum this is hydrogen s red line listed as 656 nm in the Bohr hydrogen atom gure on the handout Chemxstxy 121 Oregon State Umversxty Worksheet 1 Notes Dr Rmth L Nafshun 1 sketch 3 canmm nhhe PTE Perindic Table nhhe Elements Identify the metal 39 39 quotStair axequot 39 Metalloxds are on the staxrcase Metalloxds are elements whxch have properties ofmetals and non39metals metalshzve39 and many others These are locatedto the left ofthe stauease nnnrmetals have Name ofNoneMetax ehum m C 6 and many others These are located to the right of the staircase How many protons neutrons and electrons are present in I 131 I is iodine Iodine is element number 53 Iodine has 53 protons and 53 electrons because it has no charge the number of protons equals the number of electrons Iodine 131 has 131 protons and neutrons Iodine131 has 131 minus 53 protons 78 neutrons How many protons neutrons and electrons are present in 11 This is the same question as Question 4 The symbol used here indicates the atomic number number of protons is 53 This fact is redundant because the letter I indicates the element is iodine and iodine has 53 protons The mass number number of protons plus neutrons is 131 By deduction 11 has 1315378 neutrons There is no charge on the species so the number of protons equals the number of electrons there are 53 electrons present Using the notation used in question 6 identify how many protons neutrons and electrons are present in and write the symbols for A 1429 131 B H3 iH C An atom with 6 protons and 6 neutrons 1 C D An atom with 92 protons and 143 neutrons 2 U E Plutonium with a mass number of 245 2 Pu Draw a picture representing the structure of an atom What is meant by electron cloud nucleus electron cloud fashion The electrons are mosmkely 6 be locatedm the deep whxte region ofspace What arethe masses and charges nfprntnns neutrnns and elemnnsv What is an amn39 am39cle mm lectron 9109383 x10 0 0005485799 Proton 1672622 x 10 1007276 1674927x1 1008665 masses Ins 1M mass on carbone12 atom Functional Groups Name Condensed Formula Example Description alkene R2CCR2 contains a CC double bond alkyne RCECR contains a CEO triple bond alcohol ROH contains 0 singly bonded to a C and a H thiOI RSH contains 8 singly bonded to a C and a H thiol alcohol Disulfide 88 contains 8 singly bonded to an S ether ROR contains 0 singly bonded to two C aldehyde RCHO contains C doubly bonded to O and singly to H ketone RCOR contains C doubly bonded to O and singly to two C hemiacetal ROCOHR contains C singly bonded to O of ether and of alcohol carboxylic acid RCOOH coogtains C doubly bonded to O and smeg to O of ester RCOOR contains C doubly bonded to O and singly to O amine N contains N bonded to C andor H amide RCONR contains C doubly bonded to O and singly to N aromatic contains a flat sixmember ring Of 1 What is meant by R in the condensed formula column
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