Pre-Lab 6: Gas Law ~ 70 ~

Transcription

1 Name: Pre-Lab 6: Gas Law Section: Answer the following questions after reading the background information at the beginning of the lab. This should be completed before coming to lab. 1. Convert the following: a) Torr Atmospheres b) 3.43 atm Torr and mmhg 2. If a balloon has an internal pressure of 2.25 atm and a volume of L, what would the new volume be if the pressure increased to 4587 torr? 3. A gas occupies 345.6mL at C with a pressure of torr, if the pressure changes to atm and the volume increased to 3.200L, what is the new temperature, in C, of the gas? ~ 70 ~

2 This page was left blank intentionally! ~ 71 ~

3 Lab 2: The Ideal Gas Law Objective: In this experiment you will discover how P, V, T, and n are related to each other for an ideal gas. Background Information: Boyle first discovered the relationship between gas pressure and volume in the late 1600's. Charles then described the relationship between a gases volume and temperature around Finally in 1811 Avogadro described the relationship between a gases volume and the number of particles in the gas. In today s three hour experiment you will use modern technology to discover for yourself these basic principals that took about 200 years to uncover! Part 1. The relationship between P and V Equipment List: Vernier LabQuest Handheld Pressure Sensor 20mL Luer Lock syringe Procedure: 1. Turn on your lab Quest or computer interface and plug in the pressure sensor. 2. Go to the sensors tab and then find the change units pull down. Set the units of the sensor to whatever units you want. 3. Now find the 20 ml syringe. 4. Pull the plunger on the syringe so it reads 5.0 ml. 5. Now use the luer lock fitting to attach the syringe to the pressure sensor. Record the pressure and volume. 6. By moving the plunger in and out, record at least four other pairs of pressure and volume. 7. Graph the results on Chart 1 at the top of the next page. Volume Raw Data Pressure ~ 72 ~

4 Chart 1. Pressure and Volume Part 2. The relationship between n and P While you might think you need to know n, the number of moles of air to do this experiment you really don t. All you need is a number that is proportional to n. The number we will use is a zorkblat. We will assume that a 10 ml unit of air in this room contains 1 zorblat of molecules. Equipment List: Vernier LabQuest Handheld Pressure Sensor 20mL Luer Lock syringe Procedure: 1. Find the white stopper with the leur-lock fitting, and press it tightly into a dry 125 ml Erlenmeyer Flask. 2. Attach one end of the luer-lock tubing to your pressure sensor and the other end to the leur lock fittings on the flask that does not have a valve on it. 3. Record the initial pressure. 4. Now fill the syringe with 10 ml of air (1 zorkblat of molecules). Place the syringe on the leurlock fitting that has the valve on it. Deliver 1 zorkblat of molecules into the flask, close the valve and record the pressure. Raw Data Zorkblats Pressure 0 ~ 73 ~

5 5. Remove the syringe, fill it with another zorkblat of molecules, Attach the syringe to the apparatus, open the valve, deliver the molecules to the flask, close the valve and record the pressure. 6. Continue this procedure until you blow out your stopper (When I tested this I blew out the stopper when I put the fifth zorkblat into the flask). 7. Graph the results in Chart 2 Chart 2. n and P Part 3. The relationship between T and P While you might think you need to know n, the number of moles of air to do this experiment you really don t. All you need is a number that is proportional to n. The number we will use is a zorkblat. We will assume that a 10 ml unit of air in this room contains 1 zorblat of molecules. Equipment List: Vernier LabQuest Handheld Pressure Sensor 20mL Luer Lock syringe Procedure: 1. Carefully dry your 125 ml flask and re-insert the plug and fittings. You will not use the syringe this time, so simply close the valve and attached the hose and pressure sensor to the other leu-lock fitting. Now clamp this into a ring-stand set up. ~ 74 ~

6 2. Get a 600 ml flask and fill it ½ full with ice, then add water until it is about 3/4 filled, and place it on a hot plate (do not turn it on yet!) 3. Use the ringstand to submerge the flask as much as possible in your water bath and put the temperature sensor in the water bath as well. Make sure the tubing and all electrical wires do NOT touch the hotplate. 4. Record the initial pressure and temperature. 5. Double check that now wires are touching the hotplate, and turn it on high. 6. You can use the temperature sensor to stir the water in the bath (Watch out for the wire!). 7. Record the pressure and the temperature about every 5 o. 8. Turn off the heat, remove the apparatus from the water bath and end your experiment after you have recorded 8-10 pairs of temperature and pressure. 9. Graph the results on chart 3 below. Temperature Pressure Chart 3. P and T ~ 75 ~

7 Gas Laws Report Sheet Part 1. Relationship between P and V Name: Partner: Section: What does chart 1 tell you about the relationship between P and V? When the volume was doubled what happened to the pressure? Part 2. The relationship between n and P What does the Chart 2 tell you about the relationship between P and n? Avogadro s Law deals with n and V, do these results agree with Avogadro s Law, given the relationship with P and V that we also know? explain ~ 76 ~

8 Part 3. The relationship between P and T What does Chart 3 tell you about the relationship between P and T? The equation for a line is y = mx+b, where m equals the slope(rise over run) and b is the Y intercept of the X axis. Write the above relationship in an equation. ~ 77 ~

9 Additional Questions: 1. A gas has an initial volume of 54.2mL and pressure of 765mmHg, if the volume shifts to 36.8mL, what is the new pressure in atm? 2. A container has a pressure of atm and a volume of 1.54mL, if the temperature is 254K, how many mole of gas are in the container? At STP a gas occupies a volume of mL, how many moles are there? ~ 78 ~