The ice-salt mixture was stirred with a stirring rod and the mercury thermometer was used to assure that the temperature dropped to -5O C or below. A large test tube was filled halfway with deionized water and placed in the ice bath. The temperature probe was placed in the middle of the water layer and “collect” was pressed in Logger Pro. The water was gently stirred with the temperature probe, making sure to keep the probe from touching the bottom of the test tube. Once the recorded temperature began to level off, the results were recorded as the freezing point of pure water.
The value was recorded in a lab notebook. For part 2 of the experiment, the van’t Hoff Factor of sodium nitrate was determined. 25mL of sodium nitrate was obtained and the concentration information recorded. A large test tube was filled 1/3 full of the solution and placed into the ice bath. The probe was placed in the test tube and the “collect” button pressed. The solution was stirred and once the temperature leveled off, the freezing point was recorded. The solution was then thawed.
This process was repeated two more times and the average freezing point temperature relative to the measured freezing point of pure deionized water was recorded. The actual and experimental van’t Hoff factor (i) was calculated using the average freezing point and then compared to the theoretical i value. For part 3, the determination of the molar mass of an unknown was determined. An unknown solution was obtained and the unknown number recorded as well as the given concentration information. The solution was frozen one time in the same way as the aforementioned procedures.
The Essay on Effects Of Salt On Freezing Point Of Water
... several solutes have on the Freezing Point of water. When a solute is dissolved in a liquid, the temperature at which that liquid freezes ... the flat part of the curve to determine the freezing temperature of the solution: Blank 4 Move the mouse pointer to the beginning ... graph. Record this value in your data table. 9. Repeat steps 3, 5, and 7-8 with the remaining 4 solutions, refreshing ...
The freezing point of the solution was recorded and through knowing that it is a covalent compound, the molar mass of the unknown solute was determined. Data: Freezing point of pure water| 0. 07°C| Sodium Nitrate concentration given| 1. 7 g NaNO3 /100g H2O| Sodium Nitrate concentration | 0. 2m| Freezing point of solution-Trial 1? Tfp | -0. 75°C0. 82°C| Freezing point of solution-Trial 2? Tfp | -0. 82°C0. 89°C| Freezing point of solution-Trial 3fre | -0. 78°C0. 85°C| Average ? Tfp of solution| 0. 853°C| Actual van’t Hoff factor (i)| i= 2. 9| Unknown Solution| 24C | Unknown Solution Concentration| 30% solute 70% solvent| Freezing point of Unknown Solution? Tfp | -2. 55°C2. 62°C| Molar Mass of Unknown | 304 g/mol| Data Analysis/Conclusions: The purpose of this experiment was to determine the freezing point of pure water, the van’t Hoff factor (i) for Sodium Nitrate, and the molar mass of an unknown solution. The procedure involved using an ice bath with a temperature below -5°C and the Logger Pro to record freezing point as the temperature levels out.
First pure water was frozen and the temperature probe from the Logger Pro was placed in the test tube until the temperature leveled off and the water froze. The freezing point was then recorded. Thereafter, a Sodium nitrate solution was frozen three times and the average change in the freezing point was used to determine i. Lastly, the freezing point of an unknown solution was using to derive the molar mass of the unknown solute. Through the results, the freezing point of pure water was found to be 0. 07°C . The average ? Tfp for the NaNO3 solution was 0. 53°C leading to an experimental i value of 2. 29. The ? Tfp for the unknown solution was found to be 2. 62°C leading to determined molar mass of 304g/mol. The results obtained were not that close to reported value. For instance the freezing point of pure water should have been 0. 00°C and not 0. 07°C. The i value for NaNO3 should have come out to 2 since there are 2 ions present however the obtained results came out around 2. 29. The experimental errors in this lab could be explained using a test tube that was not properly cleaned or completely dry.
The Essay on Boiling Point Impurities Water Pressure
Regelation is the fusion of two blocks of ice by pressure, or the "successive melting under pressure and freezing when pressure is relaxed at the interface of two blocks of ice." It is a phenomenon in which water refreezes to ice after it has been melted by pressure at a temperature below the freezing point of water. This pressure makes an ice skate form a film of water that freezes once again ...
Water or other chemicals in a test tube could skew the results. An i value that is lower that 2 can be explained because the van’t Hoff factor is normally lower than expected when experimentally determined. The ions will sometimes act as an ion pair leading to the lower i value. However, the higher i value obtained is abnormal and could result from an introduction of another ion through an unclean test tube or the temperature probe from the Logger Pro hitting the bottom of the test tube while recording the data.
During the experiment, both the pure water and sodium nitrate solution experienced supercooling. Through stirring the solution, an accurate freezing point was recorded, however an experimental error such as this could also have factored into the erroneous results. The method used to determine the results is sound when correct measures are taken to ensure a limited chance for experimental error. The freezing point of the pure water, sodium nitrate solution, and unknown solution can be used to determine an experimental i value or molar mass for said solution successfully.
