## Question

Mass NaCl needed:

9. Based on the actual mass of NaCl you used (#1), determine the theoretical freezing point of the ice/ saltwater bath:

Theoretical freezing point:

10. Determine the % error for the temperature of your ice/saltwater bath (comparing the temperature you measured, #2, and the theoretical freezing point, #9):

(temperature) measured - (temperature) theoretical

% error = ------------------------------------------------------------------------ X 100 Equation 14

(temperature) theoretical

% Error:

II. Molar mass determination of ethylene glycol: cooling curve for pure water

11. Plot cooling curve (temperature VS. time) for water (data in #4):

12. Use a straightedge the data (e.g., a ruler) to draw two straight lines on each cooling curve-one drawn make through the region points after before the the water freezes, and one drawn through the data points that to the y-axis).

The intersection of these two lines is the freezing point (determine by extrapolating this point up water begins freezing (e.g., the region where the curve plateaus).

Freezing point of water:

Trial 1:

Trial 2:

Average:

13. Determine the % error for the freezing point of water (comparing the average temperature you determined in #12 and the actual freezing point; NOTE: use Kelvin):

% Error:

III. Molar mass determination of ethylene glycol: cooling curve for aqueous ethylene glycol solution

14. Mass of water:

Trial 1:

Trial 2:

15. Molality of aqueous ethylene glycol solution:

Trial 1:

Trial 2:

16. Plot cooling curve (temperature vs. time) for water (data in #7):

19. The actual molar mass of ethylene glycol is 62.07 g mol-1. Calculate the % error for your average molar mass:

% Error:

Reflection Questions

1. Provide possible reasons for the % error in the temperature of your ice/saltwater bath (#10, Analysis section):

3. Provide possible experimental errors to explain the % error in your Ti of water (#13):

5. Provide possible experimental errors to explain the % error in your calculated molar mass of ethylene glycol (#19):

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