Molar Mass Of An Unknown Compound Using Freezing Point Depression

Purpose: To learn about the international system of units (SI), to become familiar with common lab equipment and techniques, to gain proficiency in determining volume, mass, length, and temperature of a variety of items using common laboratory measurement devices, to learn to combine units to determine density and concentration, and to use laboratory equipment to create serial dilutions and determine the density and concentration of each dilution.

melting produced a drop in pipette readings. For each gram of ice that melted, the volume change

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.

Other substances that dissolve in water also lower the freezing point of the solution. The amount by which the freezing point is lowered depends only on the number of molecules dissolved, not on their chemical nature. This is an example of a colligative property. In this project, you'll investigate different substances to see how they affect the rate at which ice cubes melt. You'll test substances that dissolve in water (i.e., soluble substances), like salt and sugar, as well as substances that don't dissolve in water (i.e., insoluble substances), like sand and pepper. Which substances will speed up the melting of the ice?

In this lab experiment our main focus was to get skillful in using tools such as the metric ruler, balances, thermometer, and graduated cylinder to capture measurements of length, mass, temperature and volume. Additionally, this lab helped us to become more familiar with the uncertainty of measurements, as well as becoming efficient with rounding our measurements to the correct numbers of significant figures. Our results are measured consistently with rounding to the closest answer we could possibly acquire as the data can tell you.

Through our data acquisition on day one our predicted values for the change in temperature of our NaCl solution in water was slightly off. This was most likely due to recording the freezing temperature sometime after the precise moment of the solution freezing. However, we predicted that as we doubled our concentration of NaCl in solution the freezing point depression would also double which is consistent with our results. Through our day one experiments we were able to better understand the ability of NaCl as a deicer by understanding how the freezing point depression changes based on concentration. We could further test these results by testing with different concentrations of NaCl.

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.

3. The volume of a fixed mass of a liquid sample increases as the temperature rises from 20 to

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.

Banin, A., & Anderson, D. M. (1974, February). WRCR1536. Effects of Salt Concentration Changes During Freezing on the Unfrozen Water Content of Porous Materials, 10(1). doi:10.1029/WR010i001p00124

The freezing point is the temperature at which a substance transfers from its liquid phase to a solid. Through comparison of the freezing points of a pure solvent (stearic acid), with those of a dilute solution, the molar mass of unknown solutes may be obtained. Water in its solid and liquid phase obtains a dynamic equilibrium (as their molecules convert between such phases at equal rates). Equilibrium can be disrupted through change in temperature or the addition of a solute. Increasing the temperature causes molecules to accelerate, prompting energy to be shifted to the solid surface and escape to the liquid phase. Increasing the quantity of solute in the liquid phase displaces some solution molecules that would have (if unimpeded) interacted

It is suspected that the freezing point is 64.1oC. Due to the short temperature plateau, It is difficult to determine if the freezing point occurs at during the interval (6:00-6:10). However, it appears to be have been the most reasonable determination for freezing point in comparison to the rest of the plot.

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.

Introduction Molar mass is a fundamental quantity of chemistry. There are multiple ways to find the molar mass of a substance experimentally; one way is to use Freezing Point Depression by using the following equation: ΔT= kf*m (Robinson, 2018). The purpose of this lab was to do just that; measure the freezing point depression of a solution when a solute is added to a solvent, and from that, determine the molar mass of an unknown substance, along with learning about the influence that solutes have on liquid properties. A concept of importance to this experiment is freezing point. According to LibreTexts, “Freezing point depression is a colligative property observed in solutions that results from the introduction of solute molecules to a solvent…and

The specific property observed in this lab was the freezing point depression caused by the additives. This is the change in the freezing point between a standard solvent and said solvent with added solutes. This changes the entropy of the system, making the properties change somewhat, lowering the freezing point itself with the addition of more solute. Hence, the term ‘freezing point depression’.