Lab Report #2 Intermolecular Forces PDF

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LAB REPORT...

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CHEM132-101 Experiment 2: Intermolecular Forces September 25, 2017

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Part A: Relative Volatilities of a Sample

#

Compound

Prediction

Observation

n-Decane

Evaporate 3rd because it has longest carbon chain and molecular weight

Evaporated 3rd*

n-Heptane

Evaporate 2nd because it has second highest chain and

Evaporated 1st*

n-Pentane

Evaporate 1st because it has smallest C.C. and M.W.

Evaporated 2nd*

1a

1a

1a

1b n-Butanol

Structure

Evaporate 3rd because highest C.C. and M.W.

Evaporated 2nd*

Ethanol

Evaporate 2nd because it has second highest chain and

Evaporated 1st*

Methanol

Evaporate 1st because it has smallest C.C. and M.W.

Evaporated 3rd*

n-Butanol

Evaporate 2nd because it has second strongest forces (one

Evaporated 2nd

Deionized Water

Evaporate 3rd because it has the strongest bonds (2 hydrogen bonding)

Evaporated 3rd

1b

1b

2

2

2 n-Pentane *Incorrect due to experimental error

Evaporate 1st because it has least strongest bonds

Evaporated 1st

!3 Part B: Relative Viscosities of Materials

Compound

Structure

Prediction

Observe @ Room Temperature

Second highest viscosity because it has a bigger M.W. than H2 O

n-Hexane

Glycerol

Deionized Water

Observe @ ~100°C

Second highest viscosity

Highest viscosity because it has strongest bonds and biggest M.W.

Highest viscosity

Highest viscosity (less viscous than Room Temp)

Lowest viscosity because it has smallest M.W.

Lowest viscosity

Lowest viscosity (same viscosity as Room Temp)

Part C: Mutual Solubilities of Liquids

Water

Water

Ethanol

n-Hexane

Ethylene Glycol

Prediction/Observation Prediction/Observation Prediction/Observation Prediction/Observation Immiscible/ Immiscible Immiscible/ Immiscible Miscible/ Immiscible Immiscible/ Miscible (pieces floating) (layer/barrier) (layers of bubbles) (Took a long time) Prediction/Observation Prediction/Observation Prediction/Observation Immiscible/ Immiscible Immiscible/ Miscible Immiscible/ Immiscible (layer/barrier) (Homogeneous) (Multiple layers)

Ethanol

Prediction/Observation Prediction/Observation Immiscible/ Miscible Immiscible/ Immiscible (layers) (Homogeneous)

n-Hexane

n-Butyl Acetate

Prediction/Observation Immiscible/ Immiscible (Thick layer on bottom)

Ethylene Glycol

Octanol

n-Butyl Acetate

Prediction/Observation Miscible/ Immiscible (layers)

Prediction/Observation Miscible/ Immiscible (layers of on bottom)

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Compound

Prediction

Observation

Molecular/Ionic

Potassium Permanganate (KnMnO4) + Deionized Water

Soluble

Soluble (homogenous purple)

Ionic

Potassium Permanganate (KnMnO4) +Hexane

Soluble

Non-soluble

Ionic

Sucrose (C12H22O11) + Deionized Water

Soluble

Soluble

Ionic

Sucrose (C12H22O11) + Hexane

Soluble

Non-soluble

Ionic

Iodine (I2) + Deionized Water

Soluble

Non-soluble (yellow)

Molecular

Iodine (I2) + Hexane

Soluble

Soluble (homogenous purple)

Molecular

Nickel (II) Sulfate Hexahydrate (NiSO4) + Deionized Water

Soluble

Soluble (green/blueish)

Ionic

Nickel (II) Sulfate Hexahydrate (NiSO4) + Hexane

Soluble

Non-soluble (green solid on bottom)

Ionic

Naphthalene (C10H8) + Deionized Water

Soluble

Non-soluble (white crystals)

Molecular

Naphthalene (C10H8) + Hexane

Soluble

Non-soluble (did not dissolve)

Molecular

Nickel (II) Sulfate Hexahydrate (NiSO4) + Iodine (I2) + Deionized Water + Hexane

Soluble

Non-soluble Layers: Purple (Iodine) Yellow/Green (Nickel (II)…) Rocks

!5 Post-Lab Questions:

1. A. There is a direct correlation between the structures and the observed volatilities. In step 1a, the compound with this largest carbon chain and molar-mass weight (10 carbons in ndecane) will evaporate the slowest when compared to a compound with the smallest carbon chain and molar-mass weight (MMW) (5 carbons in n-pentane). In Step 1b, all the compounds have an —OH group attached to a carbon; however, the carbon (and — OH group) with the highest carbon chain and MMW will evaporate the slowest (nbutanol) when compared to that with the smallest compound chain and MMW (methanol). B. In step 1a, the intermolecular forces (IMF) are dispersion forces. In step 1b the IMFs are dispersion, dipole-dipole, and hydrogen bond interaction. There is a correlation between IMFs and volatilities as the stronger the IMF and bigger the MMW, the longer the compound will take to evaporate. C. The IMFs present in step 2 are dispersion in all (3 molecules), dipole-dipole, and hydrogen bonding interaction. In n-Butanol there are dipole-dipole interactions and one hydrogen bond (—OH), while in deionized water, there are two hydrogen bonds attached to the oxygen. The additional structure feature that can be observed is the hydrogenbonding interaction. This bond is the strongest bond within IMF so therefore, one can predict that the compound with the most hydrogen bonds will take the longest to evaporate.

!6 2. In Part B, there is a correlation between the type and strength of a compound IMF and its viscosity. Within these three compounds, the IMF of focus is hydrogen bonding interactions. When comparing n-Hexane to glycerol and deionized water, n-Hexane does not have any hydrogen bonding forces (only dispersion forces), which makes it the least viscous compound out of the 3 listed. Glycerol has one more hydrogen bond (—OH group) than demonized water. Therefore one can infer that the molecule with the most hydrogen bonds will be the most viscous. 3. In Part C, there is a relationship between the type of IMF and the miscibilities of the liquids. Compounds with the same types of IMF are more likely to be miscible with one another. For instance, Ethanol and n-butyl Acetate as they both have dispersion, dipole-dipole, and hydrogen bonds present. However, when compounds start to have stronger or weaker IMFs than the other, than they become immiscible. For instance, deionized water contains hydrogen bonds whereas n-Hexane does not. 4. In Part D, the strongest IMF in each of the five compounds is dispersion force. The relationship between IMF and solubilities is that when a non-polar molecule/compound with dispersion forces mixes with polar molecules with dipole-dipole and/or hydrogen bonding, then they became immiscible. However, when two non-polar (ex. iodine + hexane) or two polar molecules (ex. sucrose and deionized water) with similar IMFs mix, they become soluble. 5. Based on the results from Part C and Part D, a general rule that can be used is if a molecule/ compound has the same polarity (either polar or non-polar) and similar IMFs, then they will be soluble. Most people use the term “like dissolves like” to express this explanation.

!7 6. Drugs come in salt-like form to make the drug water-soluble and maximize the body’s absorption rate. These drugs need to have simple IMFs in order to be broken down by the body and absorbed easily. These forces may include dispersion, dipole-dipole, and hydrogen bonding to make it water-soluble. 7. Procedure: 1. Place the mixture of n-Octane, sodium chloride, and water into a 100-250mL beaker. 2. Place the beaker into an ice-bath use a thermometer to measure the temperature. 3. At 0°C, the sodium chloride will form more of a precipitate. Using a funnel with funnel paper, pour the solution over the paper in order to separate sodium chloride from the mixture. 4. Now take the beaker and place it on a hot plate with a thermometer. 5. Heat the beaker to 100°C to allow the water to boil and evaporate. Do not exceed 125°C or the n-Octane will boil and evaporate as well. 6. Cool the beaker (to determine how much n-Octane is present) and the mixture will be separated....