CHEM 1AA3 Lecture Notes - Lecture 16: Horse Length, Methanol, Hydrogen Bond

51 views5 pages

indigomule819

22 Sep 2016

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Determination of vapour pressure for water, ethanol and methanol. The purpose of this lab is to determine the vapour pressure of water, ethanol and methanol. A microscale setup will be used to collect data and subsequently, a plot of vapour pressure versus temperature will be used to compare any structure-vapour pressure relationships that may exist. A microscale setup is used to measure the vapour pressures. For a detailed description of the procedures, please refer to lab manual, experiment 10 determination of vapour pressure for. Please turn to lab notebook page 45 at the end of this report. Vair = v1 + v2 = 1. 833*10-4l + 0l = 1. 833*10-4l. Vtotal = v1 + v3 = 1. 833*10-4l + 7. 0*10-5l = 2. 533*10-4l. T = 273. 15 + 60 c = 333. 15k nair = (patm*vair)/(r*tinitial) Vapor pressure is defined as the pressure of a vapour when it is in equilibrium with its non-vapour phrases.

Related Questions

Please give me Post lab questions 2 and 3 at the bottom.

Experiment 7 - Molar Mass of a Volatile Liquid

Introduction. Given the mass of vapor at conditions of known pressure, volume, and temperature, one can determine the molar mass of the vapor. The Ideal Gas Law mathematically relates the quantities of pressure (P in atm), volume (V in liters), and temperature (T in Kelvin) and the quantity of gas (n in moles). Using the expression PV=nRT where R equals the Ideal Gas Constant 0.0821 L*atm/K*mol, one can determine the quantity of gas under given conditions of pressure, volume and temperature. The number of moles of gas is found by

n =

Because the molar mass (MM) is defined as the mass of one mole of substance in units of g/mol, the molar mass of the vapor can be determined by

MM= mass of vapor in grams/moles of vapor

In this experiment, an unknown volatile liquid is heated in a boiling water bath and is vaporized. The vapor forces air from the flask until the pressure within the flask equals the barometric pressure of the lab. As with all gases, the vapor occupies the entire volume of its container. The temperature of the vapor equals the temperature of the boiling water bath. After 8-10 minutes, the vapor is cooled. The mass of the condensed liquid is determined and the molar mass is calculated as described above.

Notes:

Check out unknown from stockroom

Record unknown number

Before weighing your condensed vapor, thoroughly dry the outside of the flask and make sure that no water is trapped under the foil cover

Do not rinse your flask with water between trials

Dispose of waste in appropriate container

Procedure. You will record your data and calculations in your lab notebook.

Obtain an unknown liquid and a 3 inch aluminum foil square. You will need two 600 or 800 mL beakers, and 3 or 4 boiling chips.

Add 3 or 4 boiling chips to the water in an 800 mL beaker and heat the water to the boiling point. Continue heating for 8 to 10 minutes after the water comes to a rolling boil. The temperature of the boiling water is 100.0^oC. This will be the temperature of the vapor. Convert the temperature to Kelvin and record in your lab notebook.

800 mL Beaker

250 mL Flask

11.

Chemical Molar Mass

1-chlorobutane 92.6 g/mol

t-butyl chloride 92.5 g/mol

trichloroethylene 131 g/mol

2-propanol 60.1 g/mol

Ethyl acetate 88.1 g/mol

n-hexane 86.2 g/mol

cyclohexane 84.2 g/mol

2-butanone 72.1 g/mol

Post Lab Questions: Answer the following questions using complete sentences. Include them after your conclusion.

1. If a lab group did not keep the flask submerged in boiling water for a full ten minutes, and some unknown never vaporized, how would that affect the calculated molar mass? In other words, would it make the calculated value too high or too low? Explain why.

2. While performing this experiment, ten lab groups have ten different unknown volatile liquids with a range of molar masses. If all lab groups have exactly the same size of flask (255 mL), and all groups took their unknown vapor to the same temperature (100.0^oC) and pressure (760.0 mmHg), how would the number of molecules within the different flasks compare? Would it vary with molar mass? How? Explain.

3. A student has determined that an unknown liquid is either 1-chlorobutane or t-butyl chloride. What other physical property(s) could be used to determine the identity of the unknown?

1. Which solvent used in the isolation of methyl benzoate is highly flammable?

2. Which main reactant(s) is of renewable feedstock?

3. Explain the role in this experiment (a) methanol (b) 95% ethanol

Preparationof MethyBenzoote Needle in septum to relieve pressure ã¼ 1. Set up and turn on a sand bath (set simmer- Condenser wrapped with wet stat at 6) before doing anything else. paper towel and pipe cleaner Connector & support rod 5 mL round bottom flask in 2. Weigh 0.5 g benzoic acid into a 5 ml round bottom flask. Add 2 boiling chips. Add 2.5 mL methanol and swirl to dissolve. Add 0.1 mL (4-5 drops) c. sulfuric acid and swirl to mix. Reflux the mixture while you make and recrystallize the ASA. NB keep the condenser jacket wet throughout the reflux. 3. 4. heating mantle Micro reflux set-up At the end of the reflux, cool the reaction mixture and transfer it to the conical tube; add 5 ml water 5. Rinse the reaction flask with 4 mL ether and add to the conical tube. Mix well. [initially your product will be an oil bubble at the bottom of the test tube. Upon mixing, it should dissolve in the ether and be in the top layer.] Remove the water with a Pasteur pipette. Add a fresh 5 mL aliquot of water, mix well, and remove the water. 6. 7. Carefully add 2 mL saturated sodium bicarbonate solution with mixing (CO, bubbles evolve) to the ether layer. Remove the aqueous layer and add a second 2 mL aliquot of sat. NaHCO3. Mix until intense bubbling stops; check the pH of the aqueous layer, it should be 9 (pH paper green/blue). Remove the aqueous layer, and wash the organic layer with 2mL saturated Nad. Remove the NaClã 8. 9. Transfer the ether layer into a clean, dry test tube, using a clean, dry dropper. Add 3 -4 CaCl2 pellets. Tilt the test tube at a 45Â° angle and rotate carefully. If the CaCl2 pellets stick together, pour the ether layer into another dry test tube and add 3-4 new CaCl2 pellets. (You may need to repeat this drying procedure 3 or 4 times). When pellets float freely and don't stick to the glass, the ether is dry. 10. Transfer the dry ether layer to a pre-weighed, dry test tube, and carefully drive off the ether with a gentle stream of compressed air. The product should be a clear, sweet smelling, viscous liquid. Weigh test tube and contents to determine yield. 11. Use 1 drop of the clean, dry product to run an IR spectrum. Use product scent, viscosity, and IR data to verify that ester was made. Note: if you do not evaporate all the ether, the product will be runny rather than viscous, will smell of ether, and the yield will be suspiciously high 12. Show your products to your demonstrator, tell him/her the weight, then discard it into the flammable waste collector. 83

I need help writing a decent conclusion. Every time I submit a lab report the professor slams my conclusion saying it needs work. She wants us to state what the results mean and if they are as expected and explain the possible reasons for variation in your results. The lab is below with data/results. Please, please help.

The Ideal Gas Equation: The Determination of Gas Constant, R

Introduction:

The purpose of this experiment is to determine the gas constant R and the percentage of KClO₃ in the KClO₃ â KCl â MnO₂ mixture using the moles of O₂, the original weight of the mixture, and the stoichiometry of the reaction. Consider a plot PV vs. nT for a gas sample where P is the pressure of the gas, V is the volume occupied by the gas, n is the number of moles of gas, and T is the temperature of the gas in Kelvin. If the temperatures and pressures fall in normal ranges, the plot will yield a straight line. Thus, PV = nRT where R is the constant of proportionality between the PV product and the nT product. The object of this experiment is to determine P, V, n, and T for a gas sample and determine the gas constant R, using the equation PV = nRT. The gas sample used will be a sample of oxygen gas generated by the MnO₂ catalyzed decomposition of KClO₃. Following is the equation of the reaction:

For decomposition of the KClO₃ in a KClO₃ â KCl â MnO₂ mixture, the mass of O₂can be determined by taking the difference between the mass of the original mixture and the mass of the residue after the decomposition. This mass is then converted to moles of O₂ using the molecular weight of oxygen. The volume of the sample will be determined by water displacement in such a way that the pressure of the sample can be determined from the barometric pressure and the vapor pressure of water. The temperature of the sample will be directly measured.

Procedure:

Assemble the equipment for the apparatus shown in figure 1. With the Florence flask filled to the neck with water, the beaker one-third filled with water, and the pinch clamp open, blow into the tube which connects to the test to create a siphon between the flask and the beaker. Reverse the siphon a few times by raising and lowering the beaker. This will fill the tube connecting the flask and the beaker with water and will also remove air bubbles from the system. Adjust the siphon such that the flask is filled to the neck with water, and close the pinch clamp.

Weigh the eight inch test tube. Add approx. 1.5 grams of the KClO₃ â KCl â MnO₂mixture to the test tube and weigh the test tube containing the mixture. Record each weight to three decimal places. (Also, be sure and record the sample number for the KClO₃ â KCl â MnO₂.)

Clamp the test tube to the ring stand, and insert the stopper as shown in figure 1. With the pinch clamp open, raise the level of the beaker such that the water level in the beaker is several inches above the water level in the flask. If a significant amount of water runs into the flask, there is an air leak in the system. If you have an air leak, it must be closed before proceeding. Equalize the pressure in the flask with atmospheric pressure by bringing the water level in the beaker to the same height as the water level in the flask. After closing the pinch clamp, empty and dry the beaker. Open the pinch clamp. A small amount of water will run into the beaker: this will not affect your results since later in this experiment, you will again equalize the pressure in the flask with atmospheric pressure. Ask your instructor to check your apparatus before proceeding.

Heat the mixture with a blue flame until the mixture first begins to melt and then solidifies again; and then heat for an additional 2 mins. (Donât heat more than 7 mins.) Allow the system to cool for 15 mins. Equalize the pressure with atmospheric pressure, as before; then close the pinch clamp and open the system. Quickly measure the temperature of the gas in the flask; also measure the volume of water in the beaker. Record the barometric pressure reading from professor. Weigh the test tube with the residue and record the mass to three decimal places.

Data/Results:

	Trial 1
Weight of test tube	41.912 g
Weight of test tube + mixture	43.343 g
Weight of mixture	1.431 g
Weight of test tube + residue	43.211 g
Weight of oxygen	0.132 g
Moles of oxygen	0.00413 mol
Temperature of water (under oxygen)	21.0 ⁰C
Temperature of oxygen	20.5 ⁰C
Barometric pressure	761.5 torr
Vapor pressure of water	18.7 torr
Pressure of oxygen	742.8 torr
Volume of water displaced	0.101 L
Gas constant, R	61.9
Mass of KClO₃ in mixture (use balanced equation)	0.338 g
% of KCLO₃ in mixture	23.6 %

CHEM 1AA3 Lecture Notes - Lecture 16: Horse Length, Methanol, Hydrogen Bond

Document Summary

Get access

Related textbook solutions

Chemistry: Structure and Properties

Basic Chemistry

Principles of Chemistry Molecular Approach

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related Documents

CHEM 1AA3 Lecture Notes - Equilibrium Constant, Potassium Thiocyanate, Thiocyanate

CHEM 212 Lecture Notes - Fractional Distillation, Distillation, Methanol

CHM120H5 Lecture Notes - Lecture 1: Freezing-Point Depression, Vapor Pressure, Boiling-Point Elevation

Related Questions