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18 Dec 2019

Experiment 3: Charles’ Law (Part 2)

Using the air in a flask, measure the change in volume with temperature.

Materials:

2-Hole Rubber stopper
250 mL Erlenmeyer flask
Thermometer
100 mL Graduated cylinder
10 mL Syringe
Syringe dispensing tip

*Microwave or stovetop
*Ice
*Water
*Water bath container

*You must provide

Procedure

Connect the syringe dispensing tip to the end of the syringe.

Set up your experiment by unscrewing the cap off the 250 mL Erlenmeyer flask. Then, press the 2-hole rubber stopper into the 250 mL Erlenmeyer flask. Push the thermometer into one of the holes in the stopper, and the syringe dispensing tip (connected to the syringe) in the remaining hole.

Create an ice water bath by filling an empty container (large enough to fit the 250 mL Erlenmeyer in it) with water and ice. The exact volumes do not matter.

Place the flask in the bath and allow the flask to cool to 0 °C (32 °F). You may need to pour additional ice around the flask to sufficiently decrease the temperature.

Monitor the temperature until the air reading in the flask is 0 °C.

Remove the flask from the ice bath and discard the ice/water from the bath container.

Allow the flask to warm to room temperature. As the flask warms up, record the volume on the syringe and the temperature on the thermometer in Table 4. The volume and temperature at room temperature are the initial (Time = 0) data. Note: The gas in the flask expands as it warms, slowly pushing the piston out of the syringe. The total volume of the gas in the system is equal to the volume of the flask plus the volume of the syringe.

Use the graduated cylinder to measure and add 100 mL of hot (but not boiling) water to the water bath container and place the flask in the warm water.

Continue to record the volume reading on the syringe and the temperature on the thermometer as the gas in the flask heats every five minutes for 30 minutes. Record your results in Table 4.

Table 4: Temperature vs. Volume Data

Syringe Volume (mL) and Temperature (°C) at Room Temperature (Step 7)

Time (minutes)

Temperature (°C)

Total Volume (mL)

0

5

10

15

20

25

Post-Lab Questions:

Graph your results as temperature vs. total volume. Draw a best-fit straight line through your data pointsand determine the formula for the line in Y = mx +b form. Don’t forget to title your graph and label your axes. You may also use a graphing software program for more accurate data plots.

According to your graph, what would the total volume be at a temperature of 70 °C? 30 °C?

How do your results demonstrate Charles’ Law? Use mathematical expressions to explain your answer.

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Related questions

Experiment 1: Calculating Rate of Reaction

In this experiment you will calculate the rate of reaction of potassium iodide and hydrogen peroxide. The order of the reaction will also be determined.

Materials:

20 mL 3% Hydrogen peroxide, H2O2
15 mL Iodine-Potassium Iodide Solution, IKI (1% Iodine, 2% Potassium Iodide)
100 mL Beaker
10 mL Graduated cylinder
100 mL Graduated cylinder
250 mL Beaker
(2) 250 mL Erlenmeyer flasks
1-Hole Rubber stopper
2-Hole Rubber stopper
(2) 3 in. Rigid tubing pieces
(1) 6 in. Rigid tubing
6 Pipettes

Stopwatch
Permanent marker
Waste beaker (any volume)
*Access to graphing software
*Access to a computer
*24 in. Flexible tubing
*Water
*10 mL Distilled water

* You must provide

*You must cut this piece of tubing into two, 12 inch pieces. (if you have not already done so).

Procedure

Preparation of Apparatus

Set up apparatus as shown in Figure 2. To do this, begin by labeling the Erlenmeyer Flasks as 1 and 2. The reaction will take place in Flask 1.

Fill Flask 2 approximately three quarters of the way full with water.

Press the 2-hole rubber stopper into the top of Flask 2. Place one three in. piece and one six in. piece of rigid tubing into each hole of the rubber stopper. This should create an airtight system.

Place the one-hole stopper on Flask 1, and fit the remaining 3 in. piece of rigid tubing in the stopper hole.

Connect Flask 1 and Flask 2 with the two, 12 in flexible tubing pieces. One piece should connect Flask 1 to Flask 2, and the second piece should connect Flask 2 to the graduated cylinder. The tubing which connects Flask 2 to the graduated cylinder should be positioned low enough to be immersed in the water in Flask 2.

Figure 2: Apparatus set-up. Note this is a sample set-up and is not drawn to scale. Your specific equipment may vary slightly.

Part A: Preparation of Reactants

Pour five mL of the IKI solution into a 10 mL graduated cylinder.

Add five mL of distilled water to the graduated cylinder to bring the total volume to 10 mL. This is the 0.5% - 1.0% (diluted) IKI solution.

Pour 15 mL of 3% H2O2 solution into a 100 mL beaker.

Add five mL of distilled water to this beaker and mix with a stir rod. This is the 2.25% (diluted) H2O2 solution.

Part B: Performing the Reaction

Remove the stopper from Flask 1 and place five mL of the 3% (undiluted) H2O2 solution and 10 mL of the undiluted IKI solution provided into the flask. Immediately replace the stopper on the flask.
Note: At this point, you should select an extra beaker (any volume) from your lab kit to use as an supplemental collection container beaker for Step 6. You do not need to use the beaker yet, but keep it in close proximity.

Swirl Flask 1 until you observe a steady dripping of water going into the 10 mL graduated cylinder. This could take 3 - 5 minutes. Check for leaks in the tubing or system if water does not start rising up the plastic tubing coming from Flask 2 and traveling towards the graduated cylinder within one minute.

Stop swirling Flask 1 when you notice the steady flow of water droplets. When you stop, the water drop -rate will significantly decrease (to around one drop every 5 - 20 seconds) and could take a few minutes to stabilize. If a steady flow of drops of water does not occur within a few minutes, swirl Flask 1 for 1 more minute and check again. Repeat this process until there is a steady flow of drops of water after you have stopped swirling Flask 1.

Quickly empty liquid that has collected in the 10 mL graduated cylinder and replace the empty cylinder back under the flexible tubing.

Allow the flow of drops to become steady again. This could take 1 - 3 mL of water.

Start timing once the drop rate is steady and the volume of water collected is at a whole number (such as three mL). Record the time in Table 1 each time 2 mL of is water displaced. Continue taking data until you have at least 10 data points (20 mL displaced).
Note: Use the extra beaker (located in Part B: Step 1) to collect additional fluid when the volume of displaced water exceeds 10 mL.

Return the collected water from your 10 mL graduated cylinder to Flask 2. Ensure the seal is air tight.

Empty, clean and dry Flask 1 and the graduated cylinder.

Repeat Steps 1 - 8 for the following trial conditions: 5 mL 3% (undiluted) H2O2 mixed with 10 mL of 0.5%-1.0% IKI solution (placed in Flask 1); and, 5 mL of 2.25% H2O2 mixed with 10 mL of 1.0%-2.0% IKI solution (placed in Flask 1). Record the data in Table 2 and Table 3, respectively.
Note: Clean the graduated cylinder and extra collection beaker before it is used to measure any additional reagents for Trial 2 or Trial 3; and, before it is used for collecting the water from the reaction in the apparatus.

Use a graphing software program to make a graph of each trial. The graph should demonstrate the relationship formed between time vs. mL of water displaced.

Find and record the slope and the inverse slope for each trial.

Table 1: 10 mL Undiluted (1.0 -2.0%) IKI and 5 mL 3% H2O2

mL water displaced

Time (seconds)

2

4

6

6

8

10

12

14

16

18

20

22

Slope:

Inverse Slope:

Table 2: 10 mL Diluted (0.5-1.0% IKI) and 5 mL 3% H2O2

mL water displaced

Time (seconds)

2

4

6

6

8

10

12

14

16

18

20

22

Slope:

Inverse Slope:

Table 3: 10 mL Undiluted (1.0 -2.0%) IKI and 5 mL 2.25% H2O2

mL water displaced

Time (seconds)

2

4

6

6

8

10

12

14

16

18

20

22

Slope:

Inverse Slope:

Calculations

Post-Lab Questions

1. Determine the order of the KI in this reaction.

2. Determine the order of the H2O2 in this reaction.

3. Calculate the rate law constant.

4. What is the overall rate law?

5. When finding the order of H2O2, why was Trial 1 and Trial 3 used?

6. When finding the order of KI, why was Trial 1 and Trial 2 used?

7. Research and identify some alternative catalysts that could be used to accelerate the decomposition of hydrogen peroxide. Evaluate these catalysts and determine which option is

I need help writing a purpose for a chemistry experiment. I feel I was always do a great job, but my professor always disagrees and I’m out of ideas. The professor wants us to summarize the introduction, and summarize what you will do in each section of the experiment and state how this work will support the goal of this experiment being longer than 1/2 a page. Please, please help me right a better purpose for the experiment below. Thanks.

Experiment 9 Molecular Weight Determination of a Pure Substance Using the Ideal Gas Equation.

Introduction:

The purpose of this experiment is to determine the molecular weight of a volatile, essentially non-polar liquid. An excess amount of pure unknown volatile liquid will be placed into a flask, whose volume will also be determined. The flask will be placed into a hot water bath, whose temperature corresponds to the temperature of the gas in the flask. The liquid will evaporate, driving out the air while the excess liquid evaporates. The pressure of the gas in the flask will correspond to the atmospheric pressure. After the excess unknown liquid has been allowed to evaporate, the flask will be stoppered, cooled, and weighed to determine the grams of the unknown liquid that will be present at the temperature of the water bath as a gas. In this experiment the ideal gas equation will be used PV = nRT = (g/M)RT where R = 0.0821 L*atm/mol*K, T = temperature in K, P = pressure in atm, V = volume in liters, n = moles of gas, g = grams of gas, and M = molecular weight of gas (in units of g/mole). Solving for the molecular weight, M: M = gRT/ PV.

If the molecular weight of a gas is to be determined, the m, T, P, and V must be determined experimentally in the lab. Even though the ideal gas equation is only an approximation of the behavior of gases, molecular weights can still be obtained within 5% of the correct values, as long as volatile non-polar compounds or compounds with only slight amount of polarity are used. For example, C, H, compounds as CH4 are essentially non-polar, whereas compounds as H2O are highly polar. Hence, the ideal gas equation would not be a good approximation for describing the behavior of gaseous water.

Procedure:

At the very beginning of the period get a one-liter beaker. Put about 800 mL (your instructor will tell you the exact amount needed) of tap water into the one-liter beaker. Put the one-liter beaker with water onto the hot plate. Set the heat setting of the hot plate to the maximum value. The water in the beaker should be boiling very lightly prior to doing the actual experiment. Therefore, after the water starts boiling in the hot water bath, it may be necessary to cut the heat setting back from highest value. This will take some time. While the water is heating, get the rest of the things needed for this experiment. The setup is shown in figure 1. Record the barometric pressure (in torr to one decimal place). Obtain the rest of the setup consisting of a 250 ml flask, properly prepared rubber stopper with glass tube and aluminum foil, a no-hole rubber stopper, thermometer, and glass stirring rod.

Make sure the 250 mL Florence (or Erlenmeyer) flask is dried (if it is not dry, rinse with 5 mL of acetone, pour off the acetone into the waste bottle in the hood, and then clamp the 250 mL Florence flask onto the ring stand in the inverted position to allow the last traces of acetone to drain out and evaporate. Place the dry no-hole stopper on the flask and weight the flask with the rubber stopper on the balance to 3 decimal places. Record this weight for the weight of the flask plus rubber stopper and moist air. Place 5 mL with a graduated cylinder of unknown liquid into the flask. Place the one-hole rubber stopper, with tube and aluminum foil in the flask. This one-hole stopper, which contains a glass tube that sticks out on the top by 3 mm and is flush with the bottom of the stopper, is covered with aluminum foil with a hole punched into the bottom where the glass tube is. This one-hole rubber stopper is already prepared for you. Push it down firmly into the flask. Remove it. Do this 2-3 times to smooth out the aluminum foil so that the stopper will go down into the flask as much as possible. Then push the stopper down so that it fits snugly but not too tightly to allow it to be removed while the flask is hot. Clamp the flask about the top lip of the Florence flask. That is, the center of the clamp goes about the rim of the flask. Push the flask as far down into the water bath as possible while holding the end of the clamp with your other hand. It is important to be sure that the water in the water bath is always at least 5 mm above there the bottom of the stopper is in the flask. More water may have to be added as some of the water evaporates during the duration of this experiment. (A beaker with hot water (extra) should be present in the hood. One or two of these beakers of hot water should be enough for everyone.) If the water level is not kept to its proper height, the liquid will condense in the upper part of the flask and the excess liquid will never be removed. Be sure that the aluminum foil on top makes a protective wind breaker for the short glass tube sticking out of the rubber stopper so that condensation does not occur there also. As the liquid evaporates from the flask, mix the water in the water bath occasionally and check to see that the temperature remains constant. Record the temperature value of the water bath as the temperature of the gas in the flask for the temperature of the gas would have equilibrated to the temperature of the water bath. After all the liquid has evaporated (takes 2-5 mins for the liquid to evaporate.) from the flask (check carefully that all of the liquid has evaporated-since observing when all the liquid has been evaporated maybe difficult, you should carefully shake slightly the clamp holding the Florence flask to observe the movement of the unknown liquid and when it has disappeared) and none is condensed on the surface walls; (if condensation occurs, be sure all precautions mentioned above are taken) then (these next several steps are to be done quick) remove the rubber stopper with the glass tubing and aluminum foil without excessive shaking. There could be a condensed liquid droplet or two in the glass tube that is not visible. The droplets could drop back into the flask and cause a false high reading for the measured weight of gas in the flask. Immediately replace the rubber stopper (with the glass tube and aluminum foil) with the no-hole stopper, which was used when the flask was originally weighed. This step must be performed quickly to prevent the unknown gas vapors from escaping and being replaced by moist air. Place the no-hole rubber stopper in the Florence flask firmly. Remove the flask from the bath and again check to be sure that the no-hole rubber stopper is firmly in place. Cool the flask by running tap water over the flask for 30-60 seconds. If the stopper is not fitted firmly, air will enter the flask as the liquid inside the flask condenses. As the gas cools and changes to the liquid state, a partial vacuum is created inside the flask. Hence, air will enter the flask if the rubber stopper is not fitted firmly. Completely dry the flask and weigh it on the balance to three decimal places. Record the weight of flask plus stopper and unknown gas.

Repeat this entire procedure a second time and record the date. After, second trial, completely fill the flask with distilled water. Place the no-hole rubber stopper in the flask allowing the excess water to overflow. Wipe the outside completely dry. Then measure the volume of the water in the flask by pouring water into a graduated cylinder. Record this volume.

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