Lab Report - Boiling Point

LAB REPORT - BOILING POINT

Objective – To investigate the relationship between the molality and the boiling point of a solution.

Hypothesis - The more benzoic acid we have in our solution, the more molality our mixture will have; this means that when we have more molality and more mass the boiling point of the solution is higher. We can prove our opinion with the next formulas:

Results

TABLE:

Mass of benzoic acid in solution (g)	Molality (mol/kg)	First run - Boiling point (oC)	Second run - Boiling point (oC)	Average boiling point (oC)	Change in boiling point compared to pure acetone (oC)
0	0	56,0	56,4	56,2	0
0.5	0,82	58,8	58,0	58,4	2,19
1.0	1,64	60,7	60,5	60,6	4,38
1.5	2,46	51,5*	51,3*	51,4*	6,57
2.0	3,28	65,3	64,7	65,0	8,76
2.5	4,10	67,1	67,1	67,1	10,95

*Here, we can see an anomaly in the data, and it does not match the pattern of the data obtained.

GRAPH:

Conclusion - As we thought, the boiling point of our solutions increases as there is more molality and more mass this happens because the relationship between the ebullioscopic constant and the molality. When we calculate the variation of the boiling point if we have more amount of the mass the change in the boiling point will be higher (higher boiling point).

Evaluation - Apparently the method of this experiment is quite good however it was difficult to measure the 5 grams of acetone accurately as the way to measure the acetone in our opinion was not the best one, so to solve this is easy, instead of us measuring the 5 grams it could already be measured.

Also we found a problem to dissolve well the benzoic acid especially when we had to dissolve higher quantities such as 2.0 grams and 2.5 grams of the acid in only 5 grams of acetone, so the solution to this would be that the quantities of the acid are a bit lower.

As the water bath was quite hot we found difficult to get the test tube out and this probably affected the results, so if we had to do it again we would improve this and the method could put to use a test tube holder to take them out with less or no problem.

As always there are human errors, for example, not dissolving the benzoic acid in the acetone which will then affect the temperature or mess up with the test tubes which will affect the results.

We have not used any references for this lab report, except from our notes or the weebly to check formulas.

ScienceSFP,. (2015). Colligative Properties. Sciencesfp.com. Retrieved 5 March 2015, from http://www.sciencesfp.com/unit-3---colligative-properties.html