Purpose:
To learn techniques for measuring the melting point, boiling point, and refractive indexes of a substance and use these measurements to identify an unknown sample.
Theory and Background: The melting point (mp) of a substance is the temperature range, which can be measured in celsius, Kelvin or Fahrenheit, where said substance moves from the solid to liquid state. If held within that range, the substance could exist in both of these states at once. If the sample is a pure solid it has a sharp mp because of the small temperature range. The new Melt-Temp apparatus was used in this experiment to measure mps. For this apparatus, the capillary tube with the sample is inserted from the side and warmed quickly until it reaches the set plateau.
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This measurement is quite sensitive to impurities and temperature because every difference within the sample will alter the path of light, effectively slowing or increasing the speed. In this experiment a Thermo 334610 Refractometer was used to find the ri of the same unknown sample used in the bp measurement. Typically ri is measured at 20℃ with the wavelength of the sodium D line. This refractometer maintains this temperature with circulating water through the upper prism. To use the refractometer, a few drops, 1-2, of the unknown should be placed on the lower prism and the upper prism then closed onto the lower one. The lamp is then fully lifted and turned on. Looking through the eyepiece, the hand wheel should be moved so that an image with a light top and a dark bottom can be seen. The compensation dial then brings the line between the 2 colors into focus and the hand wheel used to bring the crosshairs on top of the image onto the focused line. Pushing the switch down, the ri scale will be shown with the crosshairs on the ri of the …show more content…
(Structures from MedLibrary, Illustrated Glossary of Organic Chemistry, Sigma-Alderich, Wikimedia, and Wikipedia)
Summary of Key Data:
Table 1: Melting Points (mp) of the Possible Unknown Samples
(Organic Chemistry 321 & 322 Laboratory Manual)
Name of Compound
Known mp (℃)
Name of Compound
Known mp (℃)
Acetamide
80
Maleic Acid
135
Vanillin
81
Urea
134
M-toluic Acid
113
4-acetamidophenol (or acetaminophen)
171
Benzoic Acid
122
Hydroquinone
172
Benzamide
128
Table 2: Collected Melting Point (mp) Data
Sample
Temperature (℃) at
1st Sign of Melting
Temperature (℃) when
Fully Melted
Known: m-toluic acid
106
109
Unknown # 26
130
134
Unknown #26 + Urea
132
134
Table 3: Boiling Points (bp) and Refractive Indexes (RI) of the Possible Unknowns
(Organic Chemistry 321 & 322 Laboratory Manual)
Name of Compound
Known bp (℃)
Known Refractive Index
Ethanol
78
1.3611
2-Butanol
99
1.3978
1-Butanol
117
1.3988
2-Methyl-1-butanol
131
1.4053
2-Ethyl-1-butanol
147
1.4220
Cyclohexanol
161
1.4641
Table 4: Collected Boiling Point (bp) Data
Reflux Method
Dennis-Thiele Tube Method
Sample
Bp (℃)
Sample
Bp (℃)
Known: Ethanol
79
Known: Ethanol
77
Unknown #15
105
Table 5: Collected Refractive Index (RI) Data
Sample
RI
Unknown # 15
The purpose of the Unknown White Compound Lab was to identify the unknown compound by performing several experiments. Conducting a solubility test, flame test, pH paper test, ion test, pH probe test, conductivity probe test, and synthesizing the compound will accurately identified the unknown compound. In order to narrow down the possible compounds, the solubility test was used to determine that the compound was soluble in water. Next, the flame test was used to compare the unknown compound to other known compounds such as potassium chloride, sodium chloride, and calcium carbonate. The flame test concluded that the cation in the unknown compound was potassium. Following, pH paper was used to determine the compound to be neutral and slightly
The primary goal of this laboratory project was to identify an unknown compound and determine its chemical and physical properties. First the appearance, odor, solubility, and conductivity of the compound were observed and measured so that they could be compared to those of known compounds. Then the cation present in the compound was identified using the flame test. The identity of the anion present in the compound was deduced through a series of chemical tests (Cooper, 2009).
6 white powders: icing sugar, cornstarch, aspirin powder, baking soda, cream of tartar and mystery powder
The purpose of this lab was to calculate the specific heat of a metal cylinder
Results: Through a melting point reading, it was determined that the product obtained was 2,4-Dibromoanisol mp 55-58 C. The products obtained by my partners, were determined to be: (p-bromoacetanilide mp 160-165 C) and (2,4,6 tribromoaniline, mp of 108-110 C) respectively.
...eases, including temperature. It is determined from the data that the reaction is more likely to have a step wise mechanism than a concerted due to the small – ΔS and a relatively large value of ΔH from the tables. Due to some errors, it is best to perform another experiment for future protocols. In addition with the variance the 35°C where at one point the absorbance levels off and then increases. In comparison to the rate constant against temperatures, at 25°C it is higher than 35 and 45. More test is required to ensure proper determination of the rate constant at those temperatures.
The initial impure mixture was tan, with large, long crystals that were white or yellow, but after the recrystallization, the pure mixture was white powder with extremely small crystals. Upon testing for the purity through melting point comparison, the melting points were 113.7°C-116.7°C and 113.85° C-116.95°C. The average temperature is then 113.85°C-116.95°C when the trials were added and divided by two.
The objective of this experiment was to identify a metal based on its specific heat using calorimetry. The unknown metals specific heat was measured in two different settings, room temperature water and cold water. Using two different temperatures of water would prove that the specific heat remained constant. The heated metal was placed into the two different water temperatures during two separate trials, and then the measurements were recorded. Through the measurements taken and plugged into the equation, two specific heats were found. Taking the two specific heats and averaging them, it was then that
Freezing Point of Naphthalene I. Purpose To determine the freezing point of a known substance, naphthalene II. Materials ringstand gas source test tube test tube clamps thermometer naphthalene Bunsen burner goggles hose stopwatch III. Procedure 1.
By doing this experiment, I can know the physical and chemical properties of these samples. After I get my results about the physical and chemical properties of these samples, I can compare my results with the information given by the past student and identify the 5 unknown samples, finding out which sample is which substance. Hypothesis = ==
The Index of refraction of a transparent object is a measure of its ability to alter the direction of a ray of light entering it. When light is passed through water it slows down, therefore when light slows down it changes direction and this is called refraction. Testing will be on finding how the angle of refraction changes in water as the amount of salt (NaCl) is increased.
Units of Temperature. Obtain a Celsius thermometer. Half-fill a beaker with tap water and place it on wire gauze supported on a ring stand. Now place the bulb thermometer in the water and read the temperature to the nearest half degree. Next warm the water until the water is almost boiling. Again take and record its temperature.
The index of refraction is defined as the speed of light in vacuum divided by the speed of light in the medium. In this experiment, the index of refraction for the perspex is 1.50. Snell's Law relates the indices of refraction of the two media to the directions of propagation in terms of the angles to the normal. It refers to the relationship between the different angles of light as it passes from one transparent medium to another. When light passes from one transparent medium to another, it bends according to Snell's law which states: [IMAGE] where: n1 is the refractive index of the medium the light is leaving, n2 is the refractive index of the medium the light is entering, sin 2 is the is the incident angle between the light ray and the normal to the medium to medium interface, sin 1 is the refractive angle between the light ray and the normal to the medium to medium interface.
0.1M HCl, 10 mL of 0.1N KMnO4, 0.2 g. KI, 5 mL of alcohol, and 5 mL of
...pplied to phase quantification only if structures of all phases are known. At the same time still a direct method, an internal standard method and relative intensity ratio (RIR) method are used. It should be noted that each of the available methods has its intrinsic limitation, so that final choice should be made based on specific task and material to be analysed.