The students investigated about freezing point depression and at what temperature the substance changes states. The students used the freezing point depression to find the molar mass of benzene acid. First they heated Laurie acid to determine the temperature that the freezing point of the solvent is and then compared the temperature to that of the Laurie acid/ benzene acid solution. They then took the change in temperature in order to determine the immolate of the benzene acid, which was calculated to be 1 mol/keg. Then they found the moles of benzene acid to be . 0805 mol. Using what they found in the experiment they compared it with the 1. 00 g of benzene acid that was added to in experiment, they found that the molar mass of benzene acid was 125. 46 g/mol. Apparatus: Materials: Laurie Acid Benzene Acid Culture Tube With Cap Safety Goggles Bunsen Burner Wire Gauze Iron Ring Spatula Blank Label Ring Stand 400-ml Beaker Thermometer Utility Clamp Paper Towels Theory: The lab focused on immolate and its relation to the temperature change of a substances freezing point depression. Students relationship found the equation elate T = K(f)x m.
Students were figure out that based on the molar mass of benzene acid added that it affected the freezing point of Laurie acid. The freezing point of the solution is depressed because the molecules of the benzene acid allowed for the bonding of the Laurie acid molecules, therefore increasing the amount of energy needed to break the bonds and decreasing the amount of energy needed to change into a solid state. Pre-lab: The students found that the 7. 98 g of Laurie acid became solid at 43. 75 degrees Celsius. When 1. 03 g of benzene acid was added in the 7. 8 g of Laurie acid the constant for the solvent in the solution was 3. 0 degrees Celsius-keg/mol. Then based on the data we calculated the molar mass of the benzene acid to be about 122 g/mol. Procedure: Activity 1: 1. Fill a 400-ml beaker with 300 ml of water and begin heating 2. Mass 8 grams of Laurie acid to the nearest 0. 01 g, record the mass, and transfer the acid to the culture tube. 3. Clamp the culture tube too ring stand 4. Heat the Laurie acid in the water bath to a minimum of 70 degrees Celsius or until liquefied. 5. Move the clamp/tube assembly out of the water. 6. Place the thermometer in the Laurie acid. Stir gently with the thermometer until the temperature reaches 60 degrees. . As soon as the temperature of the Laurie acid reaches 60 degrees Celsius, start recording the temperature every 30 seconds. Maintain a constant stirring motion with the thermometer to ensure that the rate of cooling remains constant. 8. Continue recording data until the temperature readings remain constant over several minutes. When you see crystals of Laurie acid forming in the solution, you have reached the freezing point of Laurie acid. 9. Move the clamp/ be/thermometer assembly back into the hot water bath and liquefy the Laurie acid once again 10. Carefully remove the thermometer from the liquid Laurie acid.
Allow any liquid drops of acid to fall back into the tube. Remove the thermometer and wipe it clean with a paper towel. Activity 2: 1. Mass 1 gram of benzene acid to the nearest 0. 01 g. Place the benzene acid in the culture tube that contains the Laurie acid from Activity 1. 2. Heat the benzene/Laurie acid mixture to 70 degrees or more, until it is liquefied. 3. Repeat steps 6-11 from Activity 1 . Data: Mass of Benzene
The results were precise because the students calculated a molar mass of benzene acid and it was very close to the actual amount. There may have been some errors from the experiment because the lab was lab out to be finished the next week. This could have been prevented if the lab didn’t take so long and the water actually boiled at a reasonable time. There weren’t many errors do to the simplifies of the lab but errors could have been fix with the students being more careful.
