Dumas Method: Molecular Weight Determination

The purpose of the experiment was to determine the molar mass of three unknown solutes by measuring the freezing point depression of a solution containing each of the unknowns. When a solute is dissolved in a solvent, the vapor pressure of the solvent is lowered. As a result of the decrease in the vapor pressure, the colligative properties change.

Different procedures were used to isolate benzil from the ether layer and benzoic acid from the aqueous layers. To isolate benzil, anhydrous MgSO4 was added to the flask containing the ether layer solution. MgSO4 removes the remaining water in the ether layer solution. After making sure that enough amount of MgSO4 present in the solution, the ether solution was filtered by using gravity filtration. During filtration, MgSO4 was removed from the solution and the ether solution was collected in 25 ml flask. To separate benzil from the filtered ether solution, the beaker containing the ether solution was heated until the ether evaporated. After letting the beaker to cool to room temperature, the mass of the beaker with the benzil crystals was measured. From the combined mass of the beaker and the benzil crystals and from the predetermined mass of the beaker, the mass of the collected crystals was calculated to be 0.266 gram.

During the experiment, a candle was lit on fire, and the fire was like any other normal fire, but until a beaker was placed over the fire, the fire dies out within a minute. When I would light a candle at home, it would burn for one hour for every one inch of wax. For a fire to burn, it needs fuel, heat, and oxygen. For that reason, the fire takes in oxygen molecules from the air for it to burn. Therefore, when a beaker is placed over a fire the oxygen supply gets limited, and the fire uses all the oxygen that remains in the beaker, but when the oxygen runs out, the fire also dies out.

The air pressure fell below the vapor pressure, and the water boiled. 10) Use your observations to compare the atmospheric pressure outside the beaker to the air pressure inside the beaker before lighting the candle. The pressure is equal before lighting the candle because the beaker took the air from outside the beaker, and nothing has been done to change the

Benzyltriphenylphosphonium chloride (0.201g) and 9-anthraldehyde (0.116g) were weighed and added to a short-neck round-bottomed flask (5ml). Dichloromethane (2ml) was measured using a measuring cylinder and added to the

After the flame of the candle was put off the condensation inside the beaker disappeared this could have happened due to environment error. Another possible error could be when the 15 mL of indicator solution Bromothymol Blue was taken from the beaker that contains the substance. The students did not have an increment of five on their beaker, the level ranged from 10-50mL when the students had to pour the substance into their 50 mL beaker they had to use common sense to figure out how much 15mL. When the students measured the substance they had to be precise, so they could get an accurate result. To see if water is part of a products of a combustion reaction practical errors like the wick of the candle was short and the wick was getting thinner, so heat could not reach the bottom of the beaker this

Distillation is a method of separating two volatile chemicals on the basis of their differing boiling points. During this lab, students were given 30 mL of an unknown solution containing two colorless chemicals. Because the chemicals may have had a relatively close boiling point, we had to employ a fractional distillation over a simple distillation. By adding a fractionating column between the boiling flask and the condenser, we were able to separate the liquids more efficiently due to the fact that more volatile liquids tend to push towards the top of the fractionating column, thereby leaving the liquid with the lower boiling point towards the bottom. After obtaining the distillates, we utilized a gas chromatograph in order to analyze the volatile substances in the gas phase and determine their composition percentage of the initial solution. Overall, through this lab we were able to enhance our knowledge on the practical utilization of chemical theories, and thus also demonstrated technical fluency involving the equipment.

The purpose of this lab was to become familiar with the three different balances and two different methods used to find the weight and mass of chemicals and compounds in the ChemLab program. The lab was performed by using three different types of balances, and the direct weighing and weighing by difference methods.

Laboratory technique 6 explains how to accurately measure an amount of a substance for use in calculations by using a scale tared to the mass of a weighing paper, before adding the object to be weighed (Beran, 2014). Two other techniques that are relevant to this experiment are 9 and 16a, which respectively describe how transferring small quantities of solids, such as the unknown, should be done by dispensing the substance into the cap of the reagent bottle before taking it elsewhere in order to avoid any excess of it, and how the volumes of liquids, such as cyclohexane, should be read at the bottom of the meniscus in order to maximize accuracy (Beran,

The purpose of this lab is to identify the molecular mass of the volatile liquid. The molecular mass needs to be identified because it is a property that helps determine a substance. Since the substance is volatile, or easily evaporated, the liquid can be converted into gas. As the substance converts into gas, the ideal gas law, PV=nRT, can be used to calculate the the number of moles. Once, the number of moles is calculated, it is used in the molecular mass equation, which is, molecular mass = grams /mol. The grams of the gas is taken directly by measuring the substance, and the moles is taken indirectly through the calculations of the ideal gas law. The result of the calculations should be the molecular mass of the substance.

3. The beaker was filled to about half full of water and used to determine its temperature to the nearest degree. Afterwards the density of the water, at that specific temperature, was obtained by means of searching the web, we recorded all of the results.

The usual boiling point for water was 100°C, but in this case the water had already started boiling at 94.5°C. This is because the blue flame that the Bunsen burner was projecting was higher in temperature than the normal orange flame. During this, the atoms that made up the water were getting more and more energized due to the blazing heat coming from the blue flame. The most energetic atoms will start trying to escape from the liquid into the atmosphere, called evaporation. The atoms in the atmosphere will try and keep the atoms fro escaping, but some atoms will still escape.

The purpose of this experiment is to identify an unknown substance by measuring the density and boiling point. I will be able to conclude which substance is my own from a list of known options stating what its real boiling point and density is.

Suppose, we are given number of molecules (Ni) and molecular weight of those molecules (Mi),

I am a 5th year PhD candidate in Chemical Engineering at the University at Buffalo. I received my undergraduate degree in May 2011 in Materials Science from the Indian Institute of Technology (IIT) Kanpur. I have been an enthusiastic researcher throughout my undergraduate studies and was awarded the Proficiency Medal for my accomplishments. I have presented my undergraduate research at several conferences and have won best poster awards. Following my undergraduate education, I worked for a year as a Research Assistant at the Nanoscience Laboratory at IIT Kanpur, which is led by Dr. Ashutosh Sharma, the Secretary of the Indian Department of Science and Technology. In the fall of 2012, I started graduate school at the University at Buffalo, where I have maintained an excellent academic record and won several awards, including the School of Engineering and Applied Sciences Dean’s Fellowship and the APS Distinguished Student Seminar Program Award.