Part 2

Student Learning Objectives

1. to understand the molecular basis for freezing point depression.

2. to be able to calculate and compare the quantitative effects of different solutes on freezing points, including recognition of the special behaviors of electrolytes.

3. to gain experience in making reasonable assumptions and estimates in addressing a complex problem.

4. to understand the colligative properties of a solution vs pure solvent.

(Freezing point) After stopping at Wawa, Tysean, Roger, and Lauren decided to stop at ACE Hardware in Greentree to pick up salt for deicing the sidewalk in front of their apartment (approximately 3ft x 10ft). Here are the prices for the different types of salt: Rock Salt - $10.00/ 10lbs Calcium Chloride - $18.95/ 10lbs Urea - $15.00/ 10lbs Whats all this?! Roger asked. I thought that all salt was the same? I dont know Tysean and Lauren both shrugged. Maybe one of these works better than the other Tysean said. Questions:

1. Draw the structure of each of these salts.

2. What is the Vant Hoff factor?

3. Which of the salts, do you think, would be the best deicing agent? Defend your answer using the chemical principles. Hint: Consider the Vant Hoff factor, cost per square foot, etc.

4. Show calculations/work.