Cognitive Properties Of An Unknown Lab Report

Title and Authors
Colligative Properties of an Unknown
Adriana Garcia and Demonta Coleman. Chemistry 112-591
Introduction
Cold-tolerant fish and animals survive the freezing waters and temperatures in which they live unlike other animals that could freeze to death due to their ability of lowering the freezing point of water in their bodies. This is due to freezing point depression, which is a colligate property, a physical property that depends on the number of solute particles in the solution. The purpose of the experiment was to determine the identity of an unknown solute by using the concept of freezing point depression.
Materials and Methods The chemicals used to perform this experiment were distilled water, sodium chloride (NaCl), ice,

The mass of an 11 dram vial was taken before and after it was filled with 15 mL of distilled water, resulting in a mass of 29.9667 grams without the distilled water and 44.7771 grams with the distilled water. The looped wire was inserted into the 11 dram vial, to be used for stirring. The 11 dram vial was then submerged into the ice bath, and the Vernier temperature probe was immersed into the 11 dram vial. Once the temperature of the distilled water reached 10°C, the temperature was recorded every 10 seconds. After the data was collected, the 11 dram vial was brought back to room temperature. Trial #2 and Trial #3 were used to determine the freezing point of an aqueous solution. The “Unknown C” was used to create the aqueous solution. For Trial #2, 2.0019 grams of “Unknown C” were weighed and dissolved into the 11 dram vial. Once dissolved, the 11 dram vial was submerged into the ice bath, and the Vernier temperature probe was immersed into the 11 dram vial as well. Once the temperature of the aqueous solution reached 10°C, the temperature was recorded every 10 seconds. The 11 dram vial was brought to room temperature after the data for Trial #2 was collected. For Trial #3, an additional 2.0066 grams of “Unknown C” were weighed and dissolved into the 11 dram vial. Once “Unknown C” was dissolved, the 11 dram vial was submerged into the ice bath, and the Vernier temperature probe was immersed into the 11

The following formula in Figure 4 was used to determine the intersection between Trial #1 and Trial #2 and Trial #1 and Trial #3.
The following formulas in Figure 5 were used to determine the depression in the freezing point was used to determine the molality of the solution, the moles of the solute present, the molar mass of the solute, and finally the unknown, in respective order.
The average experimental mass was 144.5 grams per mole as shown in Figure 6, which is a 20% error from the accepted molar mass of glucose 180.16 grams per mole as is shown in Figure 7. Errors could have come from the ice bath not being cold enough, not all the powder transferred into the 11 dram vial, and not dissolving all of the powder. The usage of tap water instead of distilled water would have affected the results for tap water contains other ions which would then affected the freezing point depression. Salting icy roads and walkways lowers the freezing point of the water that forms ice which leads to melting and prevents falling snow or rain from being able to freeze.