CHM1020 Week 7

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Chemistry

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Jan 9, 2024

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Name(s):____________________________ CHM 1020 W7 Week 7 Assignment A. Watch Boyle’s Law and answer questions pertaining to it: https://www.youtube.com/watch?v=N5xft2fIqQU 1. In this demonstration, did the volume of the balloon increase or decrease? Increase 2. What relationship is being demonstrated in this experiment? Establishes a relationship between pressure and volume 3. In this demonstration, did the volume of the marshmallow peep increase or decrease? Explain your answer: As the volume increased the peep expanded to equalize the pressure 4. Why does the volume of the shaving cream increase when Pressure is dropped (or lowered)? The air is trapped inside the mixture B. Watch both demonstrations of Charles Law and answer questions pertaining to them. (1) https://www.youtube.com/watch?v=Gi5wPnkBEYI (2) https://www.youtube.com/watch?v=5M8GR6_zIps 1. In the first demonstration, what chemical was used to demonstrate the Charles law. Why was it used? Liquid nitrogen was used. This was so that the pressure of the balloon would slow down and the balloon would contract. Once the balloon was removed it expanded until the pressure was equal on the outside and the inside 2. In the second demonstration what pressure was used to demonstrate Charles law? A constant atmospheric pressure In the second demonstration, why did the water rise in the flask after it was inverted into the beaker filled with water? The water rose because the gas was cooling and the atmospheric pressure caused pushed the water causing it to rise. 3. In the second demonstration, how much water was collected in the flask that was inverted into the beaker filled with water? 26.5mL C. Watch the demonstration of Gay-Lussac’s Law and answer questions pertaining to it: https://www.youtube.com/watch?v=1pVVZGOBIVg 1. When the Gay Lussac’s device was inserted in boiling water, what was the pressure that was recorded? 948mm Hg 2. What happened to the pressure of the gas in the Gay Lussac’s apparatus when it was dipped in regular water + boiling water? Did it increase or decrease? The pressure decreased 3. In this experiment which of the following relationships are being tested? a. Relationship between Volume and Temperature

Name(s):____________________________ CHM 1020 W7 b. Relationship between Volume and Pressure c. Relationship between Pressure and Temperature D. Watch the demonstration of Boiling water until it freezes under vacuum: https://www.youtube.com/watch?v=y4BGV7-1lhs 1. In this video demonstration, which of the following variables were lowered (or changed) to get water to boil? a. Volume b. Pressure c. Temperature 2. When pressure dropped did the boiling point of water increase or decrease? Decrease 3. Did the water freeze in this demonstration and if it did at what temperature did it freeze? It froze at -10 C and the chamber was at 15 C 4. If the temperature increases, does the water vapor pressure increase or decrease? Increase 5. In this demonstration, at what pressure did the ice crystals start to form in the beaker? 3-4mm Hg 6. In this demonstration as soon as vacuum was applied, bubbles were first visible that left the beaker. What molecules were escaping water? Dissolved oxygen 7. In the second experiment what molecule was added to water to make water boil smoothly (Carbon) Charcoal 8. What was the name of the desiccant that was used in this demonstration and what was the purpose of using the desiccant? Magnesium Sulfate, Hydris(?), and Calcium Sulfate. They are used to absorb any water vapor. 9. Give another example where a desiccant is used. Disiccants are used in every day items such as beef jerky and shoes 10. Breathing is an example of which of the following gas laws? a. Charles Law b. Boyle’s Law c. Gay Lussac’s law d. Dalton’s Law 11. A hot air balloon is a demonstration of which of the following gas laws? a. Charles Law b. Boyle’s Law c. Gay Lussac’s law d. Dalton’s Law

Name(s):____________________________ CHM 1020 W7 MATH PROBLEMS: Show your work for these numerical problem items 1-7. 1. A sample of gas has a volume of 6.20 L at 20°C at a pressure of 1.10 atm. What is its volume at the same temperature and at a pressure of 0.925 atm? (Hint: What equation will you use if the temperature is constant?). P1 = 1.10 atm P2 = 0.925 atm V1 = 6.20 L V2 = ? T = constant Using formula P1V1 = P2V2 V2 = P1V1/P2 Put value : V2 = 1.10 x 6.20 /0.925 V2 = 7.37 L 2. A gas syringe at 20°C contains 20.0 mL of CO2 gas. The pressure of the gas in the syringe is 1.0 atm. What is the pressure in the syringe at 20°C if the plunger is depressed to 10.0 mL? P1 = 1 atm P2 = ? V1 = 20 ml V2 = 10 ml Using formula P1V1 = P2V2 because temperature is constant : 1 atm x 20 ml = P2 x 10 ml P2 = 20/10 = 2 P2 = 2 atm 3. A sample of the inhalation anesthetic gas Halothane, in a 500-mL cylinder has a pressure of 2.3 atm at 0°C. What will be the pressure of the gas if its temperature is warmed to 37°C (body temperature)? (Hint: Which law will you apply if the volume is constant?) P1 = 2.3 atm P2 = ? T1 =0 o C = 273 K T2 = 37 o C = 273 + 37 = 310 K if volume constant then formula will be : P1/T1 = P2/T2 2.3 atm / 273 K = P2/310 K P2 = 2.3 x 310 / 273 P2 = 2.6 atm 4. A certain quantity of helium gas is at a temperature of 27°C and a pressure of 1.00 atm. What will the new temperature be if its volume is doubled at the same time that its pressure is decreased to one-half its original value? (Hint: Three variables have been given so what equation will you use?) P1= 1.0 atm P2 = 0.5 atm T1 = 300 K T2=?

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Name(s):____________________________ CHM 1020 W7 V1=V1 V2=2V1 T2 = T1 P2 V2/P1 V1 300K 0.5atm 2V1/1atm V1 T2=300 K 5. A 26.4-mL sample of ethylene gas, C2H4, has a pres- sure of 2.50 atm at 2.5°C. If the volume is increased to 36.2 mL and the temperature is raised to 10°C, what is the new pressure. (Hint: Three variables have been given so what equation will you use?) P1 V1/T1 = P2 V2/T2 2.5 x 26.4/275.5 = P2 x 36.2/283 P2=1.87 atm 6. A sample of a gas at 77°C and 1.33 atm occupies a volume of 50.3 L. How many moles of the gas are present? (Hint: Since moles have been asked, which equation has the moles listed in the equation. Use that to solve this problem). T=77C = 77+273 = 350 K P = 1.33 atm V=50.3L PV=nRT n= PV/RT = 1.33 x 50.3 / 0.0821 x 350 n=2.32 mole 7. A hyperbaric chamber has a volume of 200. L. (a) How many moles of oxygen are needed to fill the chamber at room temperature (23°C) and 3.00 atm pressure? (b) How many grams of oxygen are needed? (Hint: Since moles have been asked, which equation has the moles listed in the equation. Use that to solve this problem. Also don’t forget to use the equation 1 mole = Formula weight or Molecular weight to calculate the grams of O2). V= 200L T=296 K P=3atm PV=nRT n=PV/RT n= 3x200 / 0.0821 x 296 n=24.69mole gram of oxygen needed = moles x molar mass 29.69 x 32 = 790.08g