This experiment sought to utilize melting point, boiling point, infrared (IR) spectroscopy, and the index of hydrogen deficiency (IHD) to identify the structures of two unknown compounds. To ensure the successful identification of the unknowns, the molecular formula for each compound was found first. What the molecular formula does is that it allows chemists to identify elements present in a compound as well as the quantity of each element. The issue with this is that there are various compounds that share the same molecular compound yet are different in reactivity and connectivity. To resolve this problem, other measures such as finding functional groups based on IR spectroscopy, determining the boiling or melting point of a compound, and identifying the bond/ring structures using IHD are taken.
IR spectroscopy measures the absorption of infrared light that corresponds to transitions among different molecular vibrations (Gilbert & Martin 2011). An IR spectroscopy is typically used to determine the presence or absence of functional groups of a given
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compound. An IR spectra has a wavelength labeled on the x-axis and a transmittance level that lies on the y-axis. Certain regions of wavelength show the presence of functional groups through peaks. For instance, a peak that appears below 1500cm-1 is referred to as the fingerprint region. The fingerprint region is often disregarded due to the fact that it only shows single bonds. In contrast, a peak observed at a wavelength above 2500cm-1 is referred to as the hydrogen stretch region. This is the area at which hydrogen bonds to oxygen, nitrogen, and carbon are observed. The boiling point and melting point of substances are not difficult to determine.
The boiling point of a substance is “the temperature at which the total vapor pressure of the liquid is equal to the external pressure” (Gilbert & Martin 2011). Boiling point is the point at which the evaporation rate of a given liquid increases as bubbles are formed. The boiling point is usually determined by “reading the thermometer during a simple distillation” (Gilbert & Martin 2011). However for the purposes of this lab, a miniscale method was used to determine the boiling point. This method requires for a liquid to be heated using the apparatus seen in Figure 1. A thermometer is placed just above the liquid at a height where the thermometer is able to measure the vapor temperature of the liquid, not the liquid itself. As the liquid heats, the temperature rises until it reaches an equilibrium where it cannot increase any
further. Unlike boiling point, the melting point of a substance is defined as “the temperature at which the liquid and solid phases exist in equilibrium with one another without change of temperature (Gilbert & Martin 2011). In other words, melting point is the temperature at which a solid changes from the solid state to the liquid state. Often times, the melting point is not recorded as a single temperature. Rather, it is measured as a temperature range from the time a drop of liquid is observed to the time at which the solid completely melts. This is known as the melting point range In order to determine the melting point, a sample is packed into a capillary tube and heated at a rate of 1-2°C per minute until the solid melts. The melting apparatus used is shown below in figure 2. The Index of Hydrogen Deficiency is known as the degrees of saturation, the maximum number of hydrogen present. The IHD is calculated from the molecular formula using equations 1, 2, and 3. Equation 1 is usually used for compounds with hydrocarbons and oxygenates; Equation 2 for compounds with Nitrogen; and Equation 3 for compounds with halogens. Each degree of saturation indicated the presence of a bond or ring. For example an IHD of 1 indicates one ring while an IHD of 4 shows that a compound has three double bonds and one ring. In the equations below, n corresponds to the number of carbons, x the number of hydrogen and halogens, and Y the number of Nitrogen.
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).
The IR spectrum that was obtained of the white crystals showed several functional groups present in the molecule. The spectrum shows weak sharp peak at 2865 to 2964 cm-1, which is often associated with C-H, sp3 hybridised, stretching in the molecule, peaks in this region often represent a methyl group or CH2 groups. There are also peaks at 1369 cm-1, which is associated with CH3 stretching. There is also C=O stretching at 1767 cm-1, which is a strong peak due to the large dipole created via the large difference in electronegativity of the carbon and the oxygen atom. An anhydride C-O resonates between 1000 and 1300 cm-1 it is a at least two bands. The peak is present in the 13C NMR at 1269 and 1299 cm-1 it is of medium intensity.
It was learned that changing the volume of the same substance will never change the boiling point of the substance. However having two different substances with the same volume will result in two different boiling points. The purpose of this lab was to determine if changing the volume of a substance will change the boiling point. This is useful to know in real life because if someone wanted to boil water to make pasta and did not know how much water to
...lt in water. Although water is generally considered to boil at 100°C (212°F), water actually boils when the vapor pressure is the same as the air pressure around the water (Physics, 2006). Because of this the boiling point of water is lower in lower pressure and higher at higher pressure. Did you know that baking cookies above 3500 feet above sea level require special cooking directons (Burt, 2004).
Atomic Absorption (AA) Spectroscopy is a quantitative analysis technique that uses the absorption of light through a flame and gaseous chemicals. AA Spectroscopy can be used for a multitude of purposes, most notably finding the concentration of one or a few elements in a compound. AA Spectroscopy can work in two different ways using an open flame and gaseous chemicals or a graphite furnace. Flame AA Spectroscopy works by taking a compound or element and disassociating it into an aqueous solution. The solution is then blown through an incredibly small nozzle which nebulizes the liquid into a very fine mist. The nebulized liquid is then blown through a flame with a very small beam of light passing through it. This light beam detects different elements in the flame and uses the known light absorbance of the element to determine the concentration of the element in the solution. The other form of AA Spectroscopy uses a graphite furnace to heat up and incinerate a sample. A solid compound is placed in the furnace which then heats up to 2000-3000 C effectively atomizing the compound and in the process turning the rest into ash. The light beam is then shot through the furnace as the solid is being heated and subsequently atomized and the machine records the absorbance rate much like the Flame AA Spectroscopy would. The difference between flame and furnace spectroscopy is in the atomization of the sample; because the Flame Spectroscopy uses pressure to atomize the compound, much of the compound is lost when sprayed
Within this lab project our group have become very comfortable with working with the cameras, specifically learning how to setup, and shoot at the proper camera focuses. This project specifically gave us an understanding of perfect exposure, over exposed and under exposed images. Adjusting the exposure time/shutter speed gives us a larger range of depth (range) rather then adjusting the f-number (f-Stop). The f-number adjusts the length of the lens compared to the diameter of the entrance of the lens. Giving us a wider range to adjust makes the camera shots easier as its faster to find perfect exposure for your image. Taking a look at our group of photos, we can see that we have an underexposed, an overexposed and one in perfect exposure. The shutter on the camera is adjusted to the length of time it stays open for within the cameras exposure settings. Doing this allows the sensor within the camera to be exposed to more or less light.
As the water began to simmer I clipped the thermometer to the side of the pot allowing the tip to rest halfway into the water. While the thermometer began reacting and the water continued to boil, I began prepping for the cold water test. Once the water
After the water, has been boiling for 10 minutes, and the temperature inside the test tube has been stable for 5 minutes, record the temperature and remove the thermometer.
Background: Refraction is opposite of reflection where it bends the light and does not "bounce" it off of something. When light changes directions it must go through one medium to another at a specific angle to be bent. This bending is called refraction. Refraction causes our brains to be tricked and see an object not in its true position. This is because of how the light is bending. Light travels through different materials at different speeds. For example through air light travels at approximetely 300,000 kilometers per second. The speed of how fast light travels depends on the denisity
By adding the antifreeze, it interfered with the vaporization of the water therefore lowering the amount of evaporation that occurred which then lowered the vapour pressure. Boiling point elevation is the difference in temperature between the boiling point of a solution and the boiling point of the pure solvent
Thickett, Geoffrey. Chemistry 2: HSC course. N/A ed. Vol. 1. Milton: John Wiley & Sons Australia, 2006. 94-108. 1 vols. Print.
The last part of experiment 5, was learning about specific gravity and temperature. Specific gravity does not have any units, it is unitless. When measuring for the temperature, we used a thermometer to calculate the Celsius of the water, 10% sodium chloride, and isopropyl alcohol. The specific gravity uses a hydrometer to measure the gravity of the liquids. Using the hydrometer, to figure out the measurements we have to look at it from top to bottom. The water for specific gravity was .998 while the temperature of it was 24
Our original hypothesis stated that changing the amount of light the plant received will affect photosynthesis. We believed decreasing the amount of light the plant received would stop photosynthesis because plants use light energy to complete photosynthesis and other cellular processes. Our group was correct in presuming that changing the amount of light a plant received would stop photosynthesis. When a plant photosynthesizes, its chloroplasts, which are located in the leaves, absorb light energy in red and blue light waves. Plants reflect the green light waves, which makes them appear green.
More than 45 million chemical compounds are known and the number may increase in million every year, without cheminformatics, the access of these huge amounts of information is very difficult.