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BIG CHILL PROJECT – 5% Goal: Build a container that keeps an ice cube from melting for the longest period of time. 1. Must be 15.0cm x 15.0cm x 15.0cm or smaller. 2. Must operate at room temperature with no electricity. 3. Must be an original creation.

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BIG CHILL PROJECT 4. Must have a opening and chamber big enough to accommodate an ice cube.

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BIG CHILL PROJECT Grade is two parts: 1. Construction - 50 pts 2. Efficiency - 50 pts Bonus points for being a top three finisher in your class, the best design in your class, ice cube lasting longer than 8 hours, and a parent signature on the blue form. DUE THURSDAY MARCH 14

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OBJECTIVES Describe the effect on a gas by a change in the amount of gas (moles), the pressure of gas, the volume of gas, and the temperature of gas. Be able to perform calculations using Boyles Law, Charles Law, and Gay-Lussacs Law. Be able to use Daltons Law of Partial Pressures in a calculation Distinguish between real and ideal gases. Be able to tell how real gases differ from ideal gases. State the ideal gas law and know what each symbol stands for Perform calculations using the ideal gas law and the combined gas law. State and use Grahams Law of Diffusion. Be able to calculate gas stoichiometry problems (volume – volume, mass – volume, volume – mass). Be able to calculate density and molecular mass using the ideal gas law formula.

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GAS LAWS Chapters 12-13

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PRESSURE (Chapter 12) Pressure is the force per unit area. Gases exert pressure when they hit the walls of their container. To measure air pressure, you might use a barometer or a manometer. A barometer measures atmospheric pressure. A manometer measures the internal pressure of an enclosed gas.

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PRESSURE There is pressure exerted by the atmosphere. At sea level this pressure is equal to one atmosphere.

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PRESSURE DEMO Fig Newtons

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PRESSURE Pressure is measured in a variety of units. UNITABBREVIATIONCOMPARE TO 1 ATM KilopascalkPa101.3 kPa Millimeters of mercury mmHg760.0 mmHg Torrtorr760.0 torr Atmosphereatm1.0 atm Pounds per square inch* psi14.7 psi *We will use all of these but psi.

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VIDEODISC Chapter 2 – Racing Hot Air Balloons 1. Why is it easier for pilots to control the vertical direction of a balloons flight than the horizontal direction? 2. Why did Julie say that a thermal is not a good word for balloonists?

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GASES (Chapter 12) Physical Properties of Gases: Gases have mass. Gas particles do not attract or repel each other. It is easy to compress gases. Gas molecules are in constant motion Gases fill their containers completely Different gases can move through each other quite rapidly. Gases exert pressure. The pressure of a gas depends on its temperature and volume.

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GASES Remember that gases consist of very small particles, the particles have large distances between them, they are in constant, rapid, random motion and have elastic collisions. Actual gases (in real life) do not obey all the suppositions stated in the kinetic-molecular theory. In order to accurately measure a gas sample, you must know the quantity of particles (moles), pressure, temperature, and volume of a gas.

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THE GAS LAWS (Chapter 13) 1. Boyles Law:V and P; inversely proportional. 2. Charles Law: T and V; directly proportional. 3. Gay-Lussacs Law: P and T; directly proportional. 4. Avogadro Principle: moles and P or V; directly proportional.

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THE GAS LAWS DEMOS – Boyles Law Chapter 7 – Breathing and Boyles Law 1. Why does the balloon expand? 2. What does this demo have to do with breathing? 3. Have you ever heard the phrase nature abhors a vacuum? What do you think it means? Cartesian Diver World record dive Balloon and bottle Artificial lung

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BOYLES LAW

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THE LAW: For a given mass of gas, at a constant temperature, the volume varies inversely with the pressure:P 1 V 1 = P 2 V 2 PRACTICE: The pressure in a 9.0 L balloon is 2.1 atm. If the volume is reduced to 5.0 L, what will the resulting pressure be? (Temperature does not change.) V 1 = 9.0 LV 2 = 5.0 L P 1 = 2.1 atmP 2 = ? atm P 1 V 1 = P 2 V 2 P 2 = P 1 V 1 = V 2

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REMINDER EVERY TIME you do a gas laws problem: 1. Write what you know and what you are trying to find 2. Write the formula 3. Plug in the numbers with units and solve with the correct number of sig figs.

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GAS LAWS DEMO Balloon and temperature change

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CHARLES LAW

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THE LAW: The volume of a fixed mass of a gas is directly proportional to its KELVIN temperature if the pressure is constant. If pressure is kept constant, then volume must change to keep temperature the same. V 1 = V 2 T 1 T 2 You must use the Kelvin temperature scale! K = °C PRACTICE: The temperature of a sample of gas is K. The gas volume is 25.0 L. What will be the new volume of the gas if the temperature is dropped to K? V 1 = 25.0 L V 2 = ? LV 2 = T 2 V 1 = T 1 = K T 2 = K T 1

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GAS LAWS Videodisc – Chapter 5 - Imploding Can 1. Why did the can implode? 2. How does the demonstration you just saw relate to a barometer? 3. How is a vacuum seal created on a jar of homemade preserves? Egg in a bottle Bulb with pressure gauge

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GAY-LUSSACS LAW

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THE LAW: An increase in temperature increases the frequency of collisions between gas particles. In a given volume, raising the KELVIN temperature also raises the pressure. P 1 = P 2 T 1 T 2 You must use Kelvin temperature scale! PRACTICE: The temperature of a sample of gas is K. The gas pressure is 1.4 atm. What will be the new pressure of the gas be if the temperature is dropped to K? P 1 = 1.4 atm P 2 = ? atmP 2 = T 2 P 1 = T 1 = K T 2 = K T 1

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REMINDER EVERY TIME you do a gas laws problem: 1. Write what you know and what you are trying to find 2. Write the formula 3. Plug in the numbers with units and solve with the correct number of sig figs.

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DO NOW Pick up handout – due tomorrow Copy problem set info - due Feb. 25 Ch. 12 #1, 2 Ch. 13 #1, 2, 5, 6, 8, 9, 11,16, 21, 26, 27, 36, 38, 39, 42 Paper towel drive ends Friday, 3:30. Balloons and Cans lab due Feb. 19.

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HINT PTV

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PUTTING IT ALL TOGETHER Simulation on gas laws: Structure and Properties of Matter

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AVOGADROS PRINCIPLE Volume: 22.4L 22.4L 22.4L Mass: 39.95g 32.00g 28.02g Quantity: 1 mol 1 mol 1 mol Pressure: 1 atm 1 atm 1 atm Temperature: 273K 273K 273K

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AVOGADROS PRINCIPLE DEMO Beach Ball

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AVOGADROSS PRINCIPLE Particles of different gases vary greatly in sizes. But size is not a factor The Law: equal volumes of gases at the same temperature and same pressure contain equal number of particles. In gas law problems moles is designated by an n. One mole of a gas has a volume of 22.4 L (dm 3 ) at standard temperature and pressure (STP). It also has 6.02 x particles of that gas.

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DALTONS LAW OF PARTIAL PRESSURES

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THE LAW: The sum of the partial pressures of all components of a gas mixture is equal to the total pressure of the gas mixture. P total = P 1 + P 2 + P 3 + P PRACTICE (Easy Type): What is the atmospheric pressure if the partial pressures of nitrogen, oxygen, and argon are mm Hg, mm Hg, and mm Hg, respectively? P total = P 1 + P 2 + P 3 P total =

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DALTONS LAW OF PARTIAL PRESSURES (Chapter 12)

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DALTONS LAW OF PARTIAL PRESSURES PRACTICE (Hard Type): A quantity of oxygen gas is collected over water at 8 C in a L vessel. The pressure is 84.5 kPa. What volume would the DRY oxygen gas occupy at standard atmospheric pressure (101.3 kPa) and 8 C. (The dry gas pressure of water at 8 C is 1.1 kPa) T 1 = 8ºCT 2 = 8ºC V 1 = 0.353LV 2 = ? P 1 = 84.5 kPa – 1.1 kPa = 83.4 kPaP 2 = kPa You must correct the pressure so that you can have the DRY gas without the water pressure added in. P 1 V 1 = P 2 V 2 V 2 = P 1 V 1 = P 2

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GAS LAWS Videodisc – Chapter 9 Scuba Diving 1. Think about your lungs as a flexible 6-liter container full of a gas at STP. How would lung volume change at a depth of 30 meters? 2. Why not increase the oxygen to 100% and go really deep? 3. What are the bends? How do divers avoid them?

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COMBINING THE LAWS From the Boyles, Charles, and Gay-Lussacs laws, we can derive the Combined Gas Law: P 1 V 1 = P 2 V 2 T 1 T 2 Mnemonic: Potato and Vegetable on top of the Table

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COMBINED GAS LAW PRACTICE: The volume of a gas measured at 75.6 kPa pressure and 60.0°C is to be corrected to correspond to the volume it would occupy at STP. The measured volume of the gas is 10.0 cm 3. P 1 = 75.6 kPaP 2 = kPaP 1 V 1 = P 2 V 2 V 1 = LV 2 = ? T 1 T 2 T 1 = 333.0KT 2 = 273 K V 2 = P 1 V 1 T 2 = ___________________________ T 1 P 2

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STANDARDS T = 0°C = 273 K V = 22.4 L (at STP) P = 1.00 atm = kPa = mm Hg = torr Remember only kPa has limited sigfigs.

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COMBINED GAS LAW PRACTICE: Correct the volume for a gas at 7.51 m 3 at 5.0°C and 59.9 kPa to STP.

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IDEAL GAS LAW Ideal Gas Equation: PV = nRT R is the universal gas constant.

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UNIVERSAL GAS CONSTANTS R = L atm mol K R = 62.4 Lmm Hg mol K R = 62.4 L torr mol K R = 8.31 L kPa mol K Why are there four constants?

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IDEAL GAS LAW Remember: 1. Always change the temperature to KELVINS and convert volume to LITERS 2. Check the units of pressure to make sure they are consistent with the R constant given or convert the pressure to the gas constant (R) you want to use.

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IDEAL GAS LAW PRACTICE: How many moles of a gas at 100.0°C does it take to fill a 1.00 L flask to a pressure of 1.50 atm? V = 1.00 L T = 100.0°C = K P = 1.50 atmR = atmL n = ? molK PV = nRT n = PV = ____________________________ = RT

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IDEAL GAS LAW PRACTICE: What is the volume occupied by 9.45g of C 2 H 2 at STP? Hint - convert grams to moles g C 2 H 2 1 mol C 2 H 2 = mol 26.04g C 2 H 2 P = 1.00 atmR = atmL V = ? mol K n = molT = 273.0K

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PRACTICE P = 1.00 atmT = 273K V = ?R = L· atm N = 0.363mol mol· K V = nRT = (0.363mol)(273K)( L· atm)= P (1.00 atm) (mol· K) = 8.14L

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GRAHAMS LAW OF EFFUSION or DIFFUSION (Chapter 12) The rate of diffusion/effusion is inversely proportional to the square root of its molar mass under identical conditions of temperature and pressure. If two bodies of different masses have the same kinetic energy, the lighter body moves faster.

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DEMO Anise and Cinnamon 1. What can we assume about the temperatures of the two oils? 2. How is temperature related to KE? 3. How doe the KE of the two oils compare? 4. What is the formula for KE?

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CALCULATIONS KE = ½mv 2 ½ m a v a 2 = ½ m c v c 2 ½ m a v a 2 = ½ v c 2 m c ½ m a = ½ v c 2 m c v a 2 m a = v c 2 m c v a 2

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GRAHAMS LAW OF EFFUSION or DIFFUSION (Chapter 12) Rate (velocity) a = Formula mass b Rate (velocity) b Formula mass a Compare ammonia and hydrochloric acid: velocity NH 3 = 36.45g/mol velocity HCl 17.04g/mol = NH 3 is 1.46 times faster than HCl

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REAL vs. IDEAL GASES The ideal gas equation, PV = nRT, is simple to use and accurately predicts gas behavior in many everyday situations. Under very high pressure, real gases have trouble compressing completely. The ideal gas law fails. Ideal gases have no volume, but real gases do.

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REAL vs. IDEAL GASES At very low temperatures, attractive forces between real gas molecules become significant and real gases liquefy. The ideal gas law can be used under ordinary conditions only.

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GAS STOICHIOMETRY We are now going to add to our MOLE CITY diagram, adding volume of a mole of gas. VOLUME 1 mol 22.4 STP 1 mole 1 mole PARTICLES MOLE MASS 6.02 x molar mass

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GAS STOICHIOMETRY PRACTICE A. Determine the volume in 2.0 moles of H 2. ?? volume = 2.0 mol H L H 2 = 1 mol H 2 = 45 L H 2

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GAS STOICHIOMETRY B. Determine the volume in 10.3 moles of CO 2. ?? volume =

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GAS STOICHIOMETRY C. Determine the moles in 251 L of O 2. ?? moles =

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GAS STOICHIOMETRY D. What volume of hydrogen gas is needed for the complete reaction between nitrogen gas and hydrogen gas to produce ammonia? You are given 5.0L of nitrogen gas. This problem involves not a mass to mass problem but a volume to volume problem. The balanced equation is N 2 + 3H 2 2NH 3

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? L H 2 5.0L N 2 N 2 + 3H 2 2NH 3

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GAS STOICHIOMETRY E. What volume of oxygen gas is needed for the complete reaction between oxygen gas and potassium chloride to produce potassium chlorate? You are given 45.0g KCl. This problem involves not a volume to volume problem but a mass to volume problem. The balanced equation is 2KCl + 3O 2 2KClO 3

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?L O g KCl 2KCl + 3O 2 2KClO 3

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HOMEWORK Ch. 13 #40-41, due tomorrow Grahams Law handout due tomorrow. Quiz is now Monday March 3. Dry Ice lab will be Friday. Giant Problem set due March 4. Test is March 5.

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Get out Gas Diffusion lab ANALYSIS and CONCLUSION: 1. Calculate the ratio of the distance moved. Since both gases moved through the glass tube in the same amount of time, the distances the gases moved can be used as a measure of the rates of diffusion of the gases. Substituting the distance (d) each gas moved for the velocity of the gas. Determine the ratio of the distance moved. Show your work. This is the experimental ratio. USE THE CLASS AVERAGE FOR THIS. d 1 = m 2 HCl = distance NH 3 traveled d 2 m 1 NH 3 distance HCl traveled

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ANALYSIS and CONCLUSION 2. Determine the true rate of diffusion for ammonia (m 1 )to hydrochloric acid (m 2 ). Use the masses from the periodic table. Write the formula and show your work. 3. How close is your experimental value to the molecular mass ratio? Calculate your percent error. Write the formula and show your work.

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GAS LAW PROBLEMS DIRECTIONS Be sure to write: What you know and where you are going (V 1, V 2, P 1, P 2, T 1, T 2, etc.) The formula Rewrite the formula to solve for the unknown and fill in the known data. Show all units. Write the correct answer with sigfigs and units.

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GAS LAW PROBLEMS DIRECTIONS For stoichiometry: write what you know and where you are going Write the balanced equation if not given. Convert to moles, do the mole ratio, and convert to what is asked for.

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Gas Law Problems #1 1. A sample of oxygen gas occupies a volume of mL at torr pressure. What volume will it occupy at torr pressure?

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Gas Laws #1 Answer V 1 = 250.0mL V 2 = ? P 1 = torrP 2 = torr Boyles Law V 2 = V 1 P 1 = (250.0mL)(740.0torr) = P 2 (800.0torr) = = mL

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DETERMINING MOLAR MASS We can use the ideal gas equation to calculate the molar mass of a gas from laboratory measurements. The molar mass formula is Molar mass, MM = mass, m/moles, n So, n (moles) is equal to: moles, n = mass, m Molar mass, MM

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DETERMINING MOLAR MASS So, if n = m/M, substitute it in the formula. The ideal gas equation can be written as PV = mRT MM = mRT MMor P V

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PRACTICE What is the molar mass of a gas if dm 3 has a mass of 7.202g at 110°C and kPa? MM =T = V =P = m =R = MM = mRT = P V

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DETERMINING DENSITY This modified version of the ideal gas equation can also be used to solve for the density of a gas. PV = nRT bcomes D = PMM RT

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DETERMINING DENSITY MM = mRT P V rewrite with m/V on one side PMM = m RT V D = m = PMMor D = PMM V RT RT

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PRACTICE Find the density of NH 3 in g/L at 752 mm Hg and 55°C. MM = T = R = P = D = PMM = RT

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PRACTICE 1. Calculate the molar mass, MM, of a gas if dm 3 has a mass of 75.0 g at 100°C and 95 kPa.

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PRACTICE 1. Calculate the molar mass, M, of a gas if dm 3 has a mass of 75.0 g at 100°C and 95 kPa. MM =?T = 373K V =150.0LP = 95kPa m =75.0gR = 8.31 L kpa mol K MM = mRT = (75.0g)(373K)(8.31L kpa) P V (95kPa)(150.0L)(mol K) = = 16g/mol

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PRACTICE 2. Determine the density of chloroform gas, CHCl 3 if a sample massing is collected in a flask with at 37°C and a pressure of 728 mm Hg.

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PRACTICE MM = g/molT = 310K R = 62.4 L mmHgP = 728mmHg mol K D = PMM = (728mmHg)(119.37g)(mol K) RT (310K)(62.4 L mmHg)(mol) = = 4.5g/L

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GAS LAWS QUIZ –MONDAY There will be six problems. Could be any from this list: Boyles/ Charles / Gay-Lussac Daltons Law of Partial Pressure Combined Gas Law Ideal Gas Law Grahams Law of Diffusion Gas Stoichiometry Extra Credit is Density or Molar Mass problem

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