Solubility Lab - gapped notes to help with the lab PDF

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Arizona State University: CHM 237: Organic Chemistry Lab I

Solubility/Miscibility/Physical Properties

IMFs (again)

1. Intermolecular Forces (IMF) and Solubility 1.1 Intermolecular Forces  I e  a of this lab we will in a more complex context.  Melting point, Boiling point and So are all understood in terms of Intermolecular Forces.  re at must be  Intermolecular forces decrease the energies of the electron energies in molecules that interact with each other because the negatively charged electrons are stabilized by even small partial positive charges.  When interacting molecules are separated, energy must be supplied to break the IMFs (energy must be added to the system) .  Te major IMFs are:

1.2 H

 Te that will dissolve in a solvent at a specific temperature is called the solubility constant, S, which has units of mol/L (moles per liter). 1

 How much solid dissolves, i.e. the concentration of a saturated solution, will depend on intermolecular force and

 We a ca de  a e, e de  e ca  deed ad entropy increases.  An poce ha inceae enop i faoable!  Sepaaion of odeed molecle in a olid, to form a solution where the molecules are randomly oriented is favored by entropy.  Even though entropy will always favor dissolution of a solid in a liquid, energy is still required (must be added) to overcome the IMFs that hold the molecules together in the solid (and also the liquids) and that "fight" entropy.  Ad so, there are

1.3 Understanding Solubility in terms of InterMolecular Forces  The IMF considerations for solubility are more complicated than for simple melting or boiling.  To understand solubility, we need to consider three kinds of IMF: 1. The IMFs between the es in the solid: 2. The IMFs between the : 3. The IMFs between the : Example 1: The solubility of naphthalene in hexane, naphthalene is very soluble in hexane.

which

Considering the three kinds of intermolecular forces (IMF): 1. Naphthalene has no dipole moment, it is non-polar, and the IMF that are broken when the naphthalene molecules separate are moderate 2. Hexane has no dipole moment, it is non-polar, and the IMF that are broken when the solvent molecules separate are weak 3. The IMF that are formed when the solid dissolves (in the solute) are moderate  The Energy required to break the IMFs in the solute and solvent is  The Energy released when the IMFs form in the solution is  Because the IMFs that are formed are similar to those that are broken when naphthalene dissolves in hexane, the or solution is negligible, and, solution formation is always anyway, therefore: Example 2: The solubility of naphthalene in water,

which is

2

)

Considering the three kinds of intermolecular forces (IMF): 1. Naphthalene has no dipole moment, it is non-polar, and the IMFs that are broken are moderate. 2. Water has hydrogen-bonding, it is polar protic, and the IMFs that are broken are very strong. 3. The IMFs that are formed when the solid dissolves (in the solute) are weak (there is no hydrogen bonding and no dipole-dipole IMFs)  The Energy required to break the IMFs in the solute and solvent are  The Energy released when the IMFs form in the solution are  Because the IMFs that are formed are weaker than those that are broken when naphthalene dissolves in water, the

for solution

Example 3: The solubility o

S, in

and, even though solutio

s 0.9 moles/liter, which i

1. Phenol has hydrogen-bonding, it is polar protic and the IMFs that are broken are strong 2. Water has hydrogen-bonding, it is polar protic, and the IMFs that are broken are strong 3. The IMFs that are formed when the solid dissolves (in the solute) are hydrogen bonding and strong  The Energy required to break the IMFs in the solute and solvent are  The Energy released when the IMFs form in the solution are  The IMFs that are formed are or solution

hen phenol dissolves in water, th and, s

,

therefore:

3

1.4 Liquid

and

Another form of

(we already understand it!)

 We aead know how to understand how two liquids would mix with each other in terms of entropy and intermolecular forces.  We  ds mix they dissolve each other, disorder and entropy increase. The IMFs in the two liquids have to be broken as the molecules separate, and new IMFs form in the mixture. Example: The mix them together

of liquid carbon tetrachloride in liquid hexane and they will dissolve, t

is

you can

e

Considering the three kinds of intermolecular forces (IMF): 1. Carbon tetrachloride has no molecular dipole moment, it has only induced-dipole IMFs, it is nonpolar, and the IMFs that are broken are weak to moderate. 2. Hexane has no molecular dipole moment, it has only induced-dipole IMFs, it is nonpolar, and the IMFs that are broken are weak to moderate. 3. The IMFs that are formed when the liquids mix are only induced-dipole, they are weak to moderate.  The Energy required to break the IMFs in the two liquids are  The Energy released when the IMFs form in the solution are  The required for mixing is

are

when the liquids mix, th nd, solution mixing is always favored by entropy anyway, therefore:

Example: The solubility of liquid hexane in liquid water (and vice versa), is extremely small, the other, these two liquids are immiscible!

Considering the three kinds of intermolecular forces (IMF): 1. Hexane has no dipole moment, it is non-polar, and the IMFs that are broken are weak to moderate 2. Water has hydrogen-bonding, it is POLAR PROTIC, and the IMFs that are broken are very STRONG 3. The IMFs that are formed when the liquids mix are weak (there is no hydrogen bonding and no dipole-dipole IMFs) 4

 The Energy required to break the IMFs in the two liquids are  The Energy released when the IMFs form in the solution are  Because the IMFs that are formed are weaker than those that are broken when the two liquids mix, th for mixing

and, even though mixing is favored by entropy:

1.5 Quantities, Masses, Moles, Volumes and Density.  This is not a very long lab, and so it is a good opportunity to spend some time learning to work with quantities of materials, using volumes, densities, weights and moles.  I  a    c  a ceca  ae ad   eae a quantity.  We  a a d  e  e e.  We  a a d  e  e e.  We  eae e  d  a cee. Lea  e a cee  a aabe  a  will use in many laboratory settings, not just organic lab.

2. What You Will Do THIS IS A SYNC SESSION LAB. PLEASE ATTEND LAB USING THE APPROPRIATE LINK FOUND ON CANVAS! 1. PRE-LAB: You must watch complete the nd also the NOTEBOOK PRE-LAB notes as summarized below. EACH STUDENT must complete ALL OF THESE before you start the lab. They will be submitted after lab on Canvas. These must be in your own handwriting and words, you cannot type and paste into your gapped notes or notebook. Your handwriting should be neat and legible. Everything in your notebook must be in black or blue INK (not pencil). All errors or changes can be crossed out, initialed, and re-written. 2. IN LAB: TAKE CAREFUL NOTES in your notebook, EACH STUDENT will need to do this. 3. POST-LAB: Complete the POST-LAB assignment. EACH STUDENT must turn in their OWN completed COPY to the proper Link on Canvas by 11:59 PM of the scheduled lab day. 2.1 Determining solubility  You will determine the difference in solubility among compounds and solvents with different polarities. The goal is to fill-in the table below (which you should have in your lab notebook) with information about how soluble each compound is in different solvents.  If all of the solid dissolves in the solvent, then it is soluble.  I a  e e de, e   partially soluble. If none of the solid dissolves, then it is insoluble.  Y  bee ee a a a  a d  de  a ecc e  a e.  You will study the solubility of three solids, (biphenyl, benzophenone and malonic acid), in four liquid solvents (hexane, diethyl ether, ethanol and water).  Place ~0.05g (a small spatula end full , e eac e de ae) of solid malonic acid into four clean small test tubes, label the tubes, and store them in a row in a test tube rack as shown in the figure below. Do the same for benzophenone and malonic acid. You will have four test tubes of each solid sample in three rows.

5

 I eac e be, add roughly 0.3 mL of each solvent (hexane, dietheyl ether, ethanol and water), as indicted in the figure  Each solid should now be mixed with each of the four different solvents.  Ge ae eac d/e e  ee  e d ded  e e. Mae bea   ab notebook about solubility and complete the solubility table in your notebook  Y d ecd ee e d  r so n the solvent, as appropriate, and add to the notebook a you think might be important or relevant.

Solid/Solvent

Table of Solubilities Diethyl ether

Hexane

Ethanol

Water

Biphenyl Benzophenone Malonic Acid

2.2 Determining Miscibility  Y  deee e deece  cb e  dee ae. Make observations about miscibility in your lab notebook, specifically state whether the two liquids are miscible, i.e. when you mix them together they form a homogeneous mixture and do not separate into two layers, or immiscible, i.e. two distinct layers form because the two liquids do not mix.  Label three clean test tubes with the mixtures you will study: Diethyl Ether/Acetone, Acetone/Water and Diethyl ether/water.  Add roughly 0.5 ml of diethyl ether to the test tubes labeled diethyl ether/acetone and diethyl/water.  Add roughly 0.5 ml of acetone to the test tubes labeled diethyl ether/acetone and acetone/water.

 Add roughly 0.5 ml of water to the test tubes labeled acetone/water and diethyl/water.  Gently shake the test tubes and make observations in your lab notebook about miscibility and fill out the miscibility table.  Y d ecd ee e e ae r immiscible, as appropriate, and add to the notebook any other observations you think might be

Solvent Acetone Water

Table of Miscibilities Diethyl ether

Acetone

2.3 Measuring Volumes and Quantities  You will use accurate measurements of weights and volumes to determine the densities of two liquids.  Y  eae accae e  e adad ab baace,  accac  d.  Y  eed  eae e e accae a  e dabe ac pettes. For this you will learn to use a micropipette. As we mentioned above, learning to use a micropipette is a valuable skill that you will use in many other laboratory settings.

 A cee a   dee a aties of liquid with high accuracy and repeatability. 6

 Te eed e  e  a ecc ae, ad e e ee  ed e, a   e  d  the pipette is transferred into the desired container. Use of a micropipette   depress plunger to the first position  d 

d  e deed cae t work with a e  Warning: Micropipettes are fragile and expensive, do not drop them or treat them roughly!  Warning: o a value

contains liquid, always the pipette down if there is any liquid remaining in the tip.  Afe

b  Warning: When you are not using the pipette and be very careful p of it!  Warning: All liquid drawn into the pipette should be p, no liquid should enter the pipette. When the pipette avoid liquid getting into the pipette body. Never lay

 Y cee ca dee a d ae  e  100 P  Y  eed   a 1000 P ).

1

P

Determining the Density of Unknown Liquid 1  I  ab eb,  a abe  eaee   Ld 1 a  be.  Abe e abe  a ace    e e e  a e e be  a small beaker. You will fill in the rest of the table as you make measurements with the unknown liquid, volume and weight.  We a e cea d e tube supported in a small beaker. Record the weight of the empty test tube and beaker in the space at the top of your table.  U e cee, dee 0.1 mL of unknown liquid 1 into the test tube. Record the total volume of liquid in the test tube in the Table.  We e e be aa. Recd the weight of the test tube/beaker and liquid in column 2 of the Table.  Deee e e  e d b bac e e  e e e be ad beae. Recd  e in column 3 of the Table.

measure weigh!

weigh!

 U e cee, dee an additional 0.2 mL of the unknown liquid 1 into the test tube. Record the new total volume of liquid in the test tube in the Table.  We e e be aa. Recd e e of the new volume of liquid in column 2 of the Table.  Deee e e  e new volume of liquid by subtracting the weight of the empty test tube and beaker. Record this weight in column 3 of the Table. 7

 U e cee, dee an additional 0.3 mL of the unknown liquid 1 into the test tube. Record the new total volume of liquid in the test tube in the Table.  We e e be aa. Recd e e of the new volume of liquid in column 2 of the Table.  Deee e e  e new volume of liquid by subtracting the weight of the empty test tube and beaker. Record this weight in column 3 of the Table.  U e cee, dee an additional 0.4 mL of the unknown liquid 1 into the test tube. Record the new total volume of liquid in the test tube in the Table.  We e et tube again. Record the weight of the new volume of liquid in column 2 of the Table.  Deee e e  e new volume of liquid by subtracting the weight of the empty test tube and beaker. Record this weight in column 3 of the Table. Table of Measurements: Unknown Liquid 1 Weight of the empty test tube/beaker = (g) Total volume Total weight Total weight of Liquid (mL) of tube/beaker/liquid (g) of liquid (g)

Density (g/mL)

After adding 0.1 mL After adding an additional 0.2 mL After adding another 0.3 mL After adding another 0.4 mL You now have four measurements that you can use to calculate density. Calculate the density (to 2 decimal places) for the four different volumes and weights of liquid according to the formula:

g) volume (mL)  Recd ee dee   Tabe. Note that the four determinations of density are similar, but not identical. Determining the Density of Unknown Liquid 2  I  ab eb,  a a abe  eaee  known Liquid 2 as shown below.  We a e cea d e be ed  a a beae. Recd e e  e e e be ad beae  the space at the top of your table.  U e cee, dee 0.5 L   Ld 2  e test tube. Record the total volume of liquid in the test tube in the Table.  We e e be aa. Recd e e  e e be/beae ad d in column 2 of the Table.  Deee e e  e d b bac e e  e e e be ad beae. Recd  e in column 3 of the Table. Calculate the density of Liquid 2 (to 2 decimal places) and record it in your Table. Table of Measurements: Unknown Liquid 2 Weight of the empty test tube/beaker = volume Total weight Total weight of Liquid (mL) of tube/beaker/liquid (g) of liquid (g)

Here is a Table of densities of Liquids.

Liquid Pentane Hexane Ethanol Pinene Ethyl Acetate Water Methyl Benzoate Glycerol Chloroform

unknown substance (there are many other better ways) but see if you determine what unknown Liquids 1 and 2 are from this Table. You will perform calculations related to density, volume, weight, moles and numbers of molecules in the post-lab, if you are not sure how to do these, check with your TA before you leave the lab!

8

(g) Density (g/mL)

Density (g/mL) 0.63 0.66 0.79 0.86 0.90 1.00 1.08 1.26 1.48

2.5 Waste Disposal  Discard used pipette ti  De  ed ac ceca (e.. bec acd, hexane) i

the hood

2.6 Safety Because this is a chemistry lab where you will be handling chemicals, accidents and contamination can happen. It is important you wear your full PPE and be conscious about your cellphone use (which is not allowed in the lab). Most lab injuries are caused by cross contamination with your gloves or splashes when transferring solvents. Sometimes  d ce  e ae caaed ad  c  ace  ade  cee. A e  constantly remind you of the proper use of PPE and lab safety procedures, if an accident/injury/incident happens and you feel any irritation due to contact with the chemicals used in this lab, you need to:  Eye contact: Rinse eyes for 15 min in the eyewash while keeping your eyes open. This can be very uncomfortable so ask for assistance to keep your eyes open and count the time. Seek immediate medical attention.  Skin contact: Rinse for 15 min in the sink or eye wash (depending on the affected area). Remove any contaminated items of clothing and shoes. Seek immediate medical attention.  Serious skin contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.  Inhalation: Get fresh air. If difficult breathing, then lose tie, belt, collar etc. Seek immediate medical attention.  Ingestion. Do not induce vomiting and Seek immediate medical attention. It is very important to try to remain calm if an accident or injury happens and immediately inform the TA to receive the appropriate care as needed.

3. Notebook Pre- and In-Lab (10 pts) 3.1 General Lab Notebook Guidelines A lab notebook is the standard way to organize, collect, and maintain data generated in lab. A well-kept lab notebook should contain all of the information necessary for a third party to reproduce the experiment and corresponding data. Te ab eb d be bd (a c eb  be)  eaed ae. A a ab notebook is not acceptable as the pages can be torn out easily. The general guidelines for setting up your lab notebook are as follows (label the pages as you go): x x Table of Contents x P the lab packet for each experiment for the details of what to include in the Pre-Lab and I Occasionally, you will make a mistake while writing in a lab notebook. This is completely acceptable. Science is messy, and you are learning. If you make a mistake, simply cross the mistake out with a single line (regardless of the size of the error), initial the line, and date it. This lets everyone who reads the notebook know that you made a mistake and that the piece of information is invalid. It is also important to use only a single line so that the original information can still be read. Other things not to do in a lab notebook include: x Adding or editing information after the lab period has ended. x x Scratching out information so it is n x Adding or removing pages. x U x Falsifying data. Learning to organize and maintain a useful lab notebook is a skill that you will use in many scientific careers.

3.2 Pre-Lab (5 pts) ...