Molar Lab Experiment

I. LIQUID - Identification of an Unknown Liquid: Using the physical properties of Solubility, Density, and Boiling Point.

Procedure: Using distilled water, premeasured containers and objects determine displacement of fluids and density of objects. Use ice and heat measure temperatures in Celsius, Fahrenheit and Kelvin.

4- chlorobenzoic acid which was the aqueous layer has a theoretical melting point of 240-243°C, the organic layer, 4-chlorobenzyl alcohol has a theoretical melting point of 68-71°C. During our experiment we were unable to collect any data for the organic

In the experiment I performed it was proven that, the moles of a solute, the volume of the solvent, and the molarity of an aqueous solution share a mathematical relationship. Solutions, solutes and molarity are all terms that are crucial to chemistry. A solution is defined as a liquid mixture in which the solute is distributed into the major component, and a solute is defined as the minor component within a solution. The molarity of a solution is the number of moles of solute per liter of solution and it is used to express the concentration of a solution. Both the solute amount and the solution volume can be determined in experiments to aid finding the solution concentration or molarity of a substance that they are included in. I state confidently

The purpose of this experiment was to determine the pKa, Ka, and molar mass of an unknown acid (#14). The pKa was found to be 3.88, the Ka was found to be 1.318 x 10 -4, and the molar mass was found to be 171.9 g/mol.

The freezing point constant (Kf) of water is 1.86 °C m-1. Each mass amount and Van’t Hoff factor was calculated then analyzed in a table.

The freezing point depression constant for water that was experimentally determined in this analysis was 0.0479 °C/m, which was derived from the slope of the trend line in Figure 4. This is significantly lower than the constant stated in the literature of 1.86 °C/m.1 The freezing point temperature determined via cryoscopy should have been much lower in the high sucrose concentration solutions.

In the third stage of this experiment, the density of a liquid was determined and compared to known standards. A 100ml beaker was filled to about half-full with room-temperature distilled water. The temperature of the water in ◦C was recorded in order to compare to known standards later. A 50ml beaker was then weighed on a scale in order to determine mass and recorded. A sample of the distilled water with an exact volume of 10ml was then placed in the 50ml beaker using a volumetric pipette. The 50ml beaker with the 10ml of water was then weighed again and the initial mass of the beaker was subtracted from this mass to obtain the mass of the 10ml of water. With the volume and the mass of the water now known, density was calculated using d = m/V and recorded in g/ml. This process was then repeated to check for precision and compared to standard values to check for accuracy. Standard values were obtained from CRC Handbook, 88th Ed.

The objectives in this laboratory were to be able to calculate the freezing point depression among three trials of unknowns, be able to correctly measure the freezing points of p-xylene, and to be able to calculate the molar masses of the unknowns by found freezing point depression values. This was done to be able to understand and apply a concept names supercooling. Supercooling is when a liquid is put far under its original freezing point and remains a liquid or gas. This happens when a substance is cooled so quickly that it’s easier for it to stay a liquid than to crystalize, until it reached its nucleation point and begins to heat up returning to its freezing point (image 4). The supercooling of p-xylene was observed in three

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.

Purpose: The purpose of this laboratory was to gain an understanding of the differences between the freezing points of pure solvent to that of a solvent in a solution with a nonvolatile solute, and to compare the two.

In a 100-mL beaker, 6.0 mL of concentrated sulfuric acid (H2SO4) was cooled to 0 ˚C and then 3.05 g of methyl benzoate (C6H5CO2CH3; density=1.08 g/mL) was added. In two different beakers, 2.0 mL of concentrated sulfuric acid and 2.0 mL of concentrated nitric acid (HNO3) were cooled in an ice bath. Both acids were mixed together and the mixture was allowed to cool in the ice bath. The mixture in the 100-mL beaker was cooled to 0 ˚C. While still remaining in the ice bath, the acid mixture was slowly added into the methyl benzoate solution by the use of a Pasteur pipet. The temperature of the solution was controlled by swirling the solution and stopping the addition of acid mixture when the temperature raised.

One milliliter of 6.00-M phosphoric acid was placed into a 125-mL Erlenmeyer flask using a volumetric pipette. Using a slightly larger pipette, six milliliters of 3.00-M sodium hydroxide was transferred into a 50-mL beaker. Then a disposable pipette was used to slowly mix the sodium hydroxide into the phosphoric acid while the solution was swirled around. Then both the beaker and flask were rinsed with 2-mL of deionized water and set aside. A clean and dry evaporating dish was weighed with watch glass on a scale. Then the solution was poured into the dish and the watch glass was placed on top. The solution was then heated with a Bunsen burner to allow for the water to boil off to reveal a dry white solid. After the dish cooled to room temperature it was once again weighed and the new mass was recorded.

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.

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)