Intermolecular Forces : London Dispersion Forces, Dipole Interactions, And Hydrogen Bonding

After each of the solids were completely dry, each was placed into a MelTemp device. The temperature at which each solid began to melt and completed melting was recorded.

Procedure: In this experiment, various chemicals were mixed together, to determine a reaction. Using two drops from chemical 1 and two drops of chemical two, unless otherwise stated, then recording the type of physical reaction or color changes that occurred.

The purpose of this lab is to test substances and to determine the physical and chemical properties of substances.

In determining the melting point range of the aspirin, a capillary tube (sealed at one end) was one-third-filled with the dried aspirin. The capillary tube and a thermometer were immersed in an oil bath. The temperature at which the solid started to melt and the temperature when the entire sample was completely liquefied were recorded as the melting point temperature range.

pH was recorded every time 1.00 mL of NaOH was added to beaker. When the amount of NaOH added to the beaker was about 5.00 mL away from the expected end point, NaOH was added very slowly. Approximately 0.20 mL of NaOH was added until the pH made a jump. The pH was recorded until it reached ~12. This was repeated two more times. The pKa of each trial are determined using the graphs made on excel.

What special bond (in water) opposes water’s molecular movement when water absorbs energy requiring water to have more heat added to raise its temperature? Hydrogen Bond.

Substance A and B were weighed; Substance A weighed 0.502 g and substance B weighed 0.503 g. Both substances were put into two different test tube with approximately 8 ml of DI water into the test tub. Substance A and B were stirred and B dissolved while A did not. This shows that B is soluble in water compared to A. Thus, shows that B is soluble in water than A. The reason why B is soluble in water is because it has a higher dipole moment than A. With a higher dipole moment, it shows that it is soluble in water since it is polar and the bonds were easily broken.

A London dispersion force is the name given to intermolecular forces in a non-polar compound. It greatly depends on the amount of electrons in a molecule. The larger/ heavier molecules have more electrons resulting in a greater attractive London force. This is because as the external force causes a temporary shift, the electrons will move to one side and it will become more negative resulting in a greater attraction. Then it will return to its previous state of the dispersion of

In order to fulfil the labs purpose, the lab was split into two parts. The first part consisted of measuring and determining the freezing point depression of the solution water. The second part consisted of measuring and determining the freezing point depression of a solution that consisted of water and an unknown solute.

A small beaker was placed under the arm of the distillation head to catch the distillate. Foil was wrapped around the neck of the round-bottomed flask and a wet paper towel was wrapped around the arm of the distillation head to create a condenser. The flask was heated gently so that the distillate dropped at a rate of two drops per minute. The temperature was recorded as every drop was collected. The distillation began at around 55.0 ℃. The distillation was stopped after 29 drops were collected to prevent the solution from being distilled to dryness. See attached data. The known boiling point of 1-butanol is 117.5 ℃ (Lemonds). The known boiling point of 1-propanol is 97 ℃ (Thiyagarajan). The known boiling point of acetone is 56 ℃ (Forss). The known boiling point of 2-butanone is 79.6 ℃ (Jiang). For unknown #3 the boiling point of the first substance seemed to be around 56 ℃ and the boiling point of the second substance seemed to be around 111 ℃. Therefore unknown #3 seemed to be a mixture of acetone and 1-butanol.

In the first part of the experiment trans-cinnamic acid began to melt rapidly at 133 °C and had completely liquefied at 135.9 °C. Urea began to melt rapidly at 133 °C, just as the trans-cinnamic acid, but had completely liquefied at 134.7 °C. Both urea and trans-cinnamic acid had true melting points of 132 °C generating a .75 percent error. The 50:50 mixture of urea and trans-cinnamic acid started to melt quickly at 98.5 °C, slowed down at 102 °C, at which point most of the compound had seemed to have melted with the exception of a few crystals, which did not melt completely until 125°C . In the second part of the experiment, the melting point of an unknown compound was measured at a fast rate, 10 °C/min, in order to obtain an estimate of the melting point of that compound, which was about 130 °C – 139 °C. At this point the suspected organic compound was benzoin, and the melting points of the two compounds, benzoin and the unknown, as well as the 50:50 mixture of each, were obtained. The unknown compound, along with the benzoin, had identical melting points of 133.7°C – 134.9°C, while the 50:50 mixture had a melting point of 133 °C – 134.3 °C. The true melting point for benzoin is 132°C, generating a .75 percent error.

Discussion: As seen in the melting point determination, the average melting point range of the product was 172.2-185.3ºC. The melting points of the possible products are listed as 101ºC for o-methoxybenzoic acid, 110ºC for m- methoxybenzoic acid, and 185ºC for p- methoxybenzoic acid. As the melting point of the sample

It’s predicted that when adding the chemical substance into the water, energy will be released or absorbed, this will be observed by a temperature change, therefore, there would be an exothermic or endothermic reaction.

An ice bath was prepared in a large beaker and a small cotton ball was obtained. 0.5 g of acetanilide, 0.9 g of NaBr, 3mL of ethanol and 2.5 mL acetic acid was measured and gathered into 50mL beakers. In a fume hood, the measured amounts of acetanilide, NaBr, ethanol and acetic acid were mixed in a 25mL Erlenmeyer flask with a stir bar. The flask was plugged with the cotton ball and placed in an ice bath on top of a stir plate. The stir feature was turned on a medium speed. 7mL of bleach was obtained and was slowly added to the stirring flask in the ice bath. Once all the bleach was added, stirring continued for another 2 minutes and then the flask was removed from the ice bath and left to warm up to room temperature. 0.8mL of saturated sodium thiosulfate solution and 0.5mL of NaOH solution were collected in small beakers. The two solutions were added to the flask at room temperature. The flask was gently stirred. Vacuum filtration was used to remove the crude product. The product was weighed and a melting point was taken. The crude product was placed into a clean 25mL Erlenmeyer flask. A large beaker with 50/50 ethanol/water

The purpose of this lab was to study colligative properties. These properties are properties that are affected when a solute is added to a solvent. Thus, the amount is important, not the actual type of substance, for the colligative properties. A couple types of this property are the freezing point and boiling point of a substance. (1)