Dalena Khothsombath *†
Group Members: James Deringer, Jeff Tanaka, and Yang Zhao
“I pledge that this report, the data in it, and interpretations are my work, except where referenced. I have neither obtained nor given aid on this assignment outside of data discussions with my lab team. “ Signed_________________________________________
A common road salt, magnesium chloride, was analyzed in the lab to test its effectiveness as a road salt. The Van’t Hoff factor of the salt and the enthalpy of dissolution when dissolved in pure water were experimentally tested to evaluate its many characteristics as a deicer. To determine the Van’t Hoff factor, the difference of temperatures of freezing water and a solution of magnesium chloride was determined. A Van’t Hoff factor average of 2.88 was found, which is close to the ideal Van’t Hoff factor value of 3. The enthalpy of dissolution was found using calorimetry. Various amounts of magnesium chloride were added to water finding the heat of reaction for each trial. Depending on how many moles of magnesium chloride were present in each solution, the enthalpy of dissolution was then calculated which gave an average of -151.45 kJ/mol making the reaction exothermic. Magnesium chloride was compared to three other road salts to determine which of the road salts was the best for Minnesota’s winter roads. Due to the ability to lower the freezing point of water, the substantial value of enthalpy change, the least cost effective, and non-harmful effects to the environment it makes the best chloride deicer out of potassium chloride, sodium chloride, and calcium chloride.
Minnesota roads are known to become increasingly dangerous once temperatures reach below 0°C. To make the roads less of a hazard in the winters, the State of Minnesota Department of Transportation has adapted to coat the roads with salts to deice the roads. Deicers are used to eliminate or reduce the amount of ice present in icy and snowy conditions. This experiment will test the effectiveness of a specific salt, magnesium chloride (MgCl2), as a deicer for Minnesota roads.
The freezing point depression of magnesium chloride in water and the heat of enthalpy of magnesium chloride in water will be tested to help in determining how effective of a deicer magnesium chloride is. The freezing point depression will be calculated by monitoring the temperature drop of different saturations of magnesium chloride in ice baths. The heat of enthalpy will be calculated by adding different masses of magnesium chloride to a calorimeter and observing the change of heat for each trial which will give information on whether the reaction of magnesium chloride and water is an exothermic or endothermic reaction. These results along with cost per kg and environmental factors will be compared to the other salts in the lab, NaCl, KCl, and CaCl2, to find which of the salts is the best for deicing Minnesota’s winter roads.
Four trials of ice baths were carried out using various amounts of magnesium chloride in each trial. All trials were performed filling up a 400 mL beaker about three fourths full of ice and adding 10.0 mL of deionized water to each 400 mL beaker of ice. Using a LoggerPro temperature probe, the initial temperature of each the ice baths were recorded to test accuracy of the temperature probe. The following masses: 2.002 g, 2.003 g (a second time) 4.003 g, 4.003 g (a second time), and 5.002 g of magnesium chloride were then poured into each beaker of ice, each mass being used for one trial each. The LoggerPro temperature probe was used to stir the solution to ensure evenly dispersion of magnesium chloride. Once the freezing point reached a constant temperature by monitoring the graph on the LoggerPro program, the value at constant determined the freezing point of depression of the new solution by...