An Exercise in Freezing Point Depression

Name ___________________________________________ Date ____________________Partner __________________________________________ TA _____________________Post-Laboratory Questions for Experiment 101. Data Treatment for Part 1a) Carry out the necessary calculations and complete the last table on Data Sheet I.b) Prepare a graph for plotting ∆T vs. molality, m for trials 0 through 4 or 5. Selecta scale such that the graph fills over half of a page. Give the graph a title andlabel the axes. (Whether the graph is done by hand or using the computer, anymissing information will result in a loss of all points for b).c) Graph your 5 or 6 data points, including DI water, and draw the best straightline through the data points. The formula for your straight line is ∆T = imK f.(An error in graphing your data points or in drawing the best straight line willresult in the loss of all points for c).d) Determine the slope of ( i x K f) and calculate “i”. Compare this to thetheoretical value of “i”. For example, we expect i ≤ 3 for MgCl 2. Show yourwork.2. Summary of ResultsUse the computer to prepare a table that summarizes the experimental results and anyother information available to your lab section on the 5 deicers. For each deicer,include as much of the following information as possible. “Average values” may referto the average of several trials, as is the case for ∆H soln, or, as in the case of ratingsurface damage, take the average of the ratings assigned by each of the groups. Youneed to submit only one table per group.a) Slope of the plot of ∆T vs molality.b) Value of “i”c) Average mass of ice melted per gram of deicerd) Solubility at 0 or 20°C (g/100 g solvent)e) Average ∆H solnin kJ/molf) Average rating of the surface damage (corrosion or scaling) of the concretesurfaces, iron bars, and iron nails10-21