Researcher

Jianbo Zhao

Objective

The objective of experiment 179 is to determine whether pure methanol density which measured with different flasks have any influence on it. And there is another experiment, we added some cinnamic acid into pure methanol that have already calculated. Besides, there are some solutions which suppose to be measured as concentration of 1.3M, 1.4M and a saturated solution (from EXP178). Thus, another objective is to measure the density of each solution in different volumes of flasks.

Procedure

1. Weight the empty volumetric flasks (2 of 1 ml, 3 of 2 ml, 2 of 5 ml and 2 of 10 ml)
2. Add pure methanol and weigh
3. Clean with acetone and dry them with blowing air for about one minute
4. Weigh 1.3M solution, wash with some 1.4M solution and weigh that then wash the empty volume flasks with some saturated solution and weigh them.

Results

Calculations
Pure methanol Measurements
Solution Measurements
Photo09221548.jpg

Pic.1 empty flasks mass measurement

Photo09221612.jpg

Pic.2 pure methanol mass measurement

Photo09221703.jpg

Pic.3 solution does not enough to measure in 10ml flask

Pure methanol density:
10ml: 0.779 +/- 0.000587
5ml: 0.7794 +/- 0.008004
2ml: 0.772 +/- 0.0121287
1ml: 0.750 +/- 0.0031820

a.Plot of mean via different volume of flasks. (Graph.1)

121.PNG
Graph.1 Mean with different volume of flasks.

b. Plot of indivadual value via different volume of flasks. (Graph.2)

exp1781.PNG
Graph.2 Indivadual value with different volume of flasks.

c.Plot of standard deviation via different volume of flasks. (Graph.3)
exp11111.PNG
Graph.3 standard deviation with different volume of flasks.

Discussion

  1. The published density of pure methanol at 25C is 0.78656 g/ml and at 20C is 0.7913 g/ml. (DDBST )
  2. All of the measured values for the density of pure methanol in this experiment are below this range.
  3. There seems to be a correlation between the flask size and mean density, with the smallest flask has the lowest measurement of the density of methanol. This might be due to undershooting the meniscus generally and the highest error would be for the smallest flask.
  4. There does not appear to be a consistent trend with respect to the standard deviation and flask size. More measurements are required.
  5. The data did not relate to exp 178. The reason for it was probably the meniscus of measuring the volume.
  6. The measurements of the solutions of known concentration were off by 6-30%, which is much higher than the maximum error of 4% in EXP178 for the same solutions. It is likely that error in reading the meniscus is at least partially the source of the larger error.

Conclusion

From the data and observation, we can conclude as follows
  1. Except 1ml, as the volume of flasks increases, the standard deviation decreases. Which mean the error decreases as the measurement volume increases.
  2. All the measured values are below the published range.
  3. There are large error of the solution cinnamic acid in pure methanol.

Log

2010-09-22

15:10 Set up equipments, measure 2 empty 10ml flasks and labels as 1A, 1B. 1A has a mass of 9.7003g and 1B is 9.7634g
15:35 measure 2 empty 5ml flasks and labels as 2A, 2B. 2A has a mass of 6.2631g and 2B has 9.9711g
15:38 measure 3 empty 2ml flasks and labels as 3A, 3B and 3C. 3A has a mass of 5.4084g and 3B has 5.6049g, 3C is 5.5936g
15:43 measure 2 empty 1ml flasks and labels as 4A, 4B. 4A has a mass of 12.7706g and 4B has 17.5978g, shows as Pic 1
15:49 Put pure methanol into 2 empty 10ml and measure the total mass. one is 17.4876g and the other one is 17.5590g. Capped them.
15:56 Put pure methanol into 2 empty 5ml and measure the total mass. one is 10.1885g and the other one is 13.8399g. Capped them.
16:00 Put pure methanol into 3 empty 2ml and measure the total mass. one is 6.9435g, one is 7.1418g and the other one is 7.1178g. Caped them.
16:07 Put pure methanol into 2 empty 1ml and measure the total mass. one is 13.5228g and the other one is 18.3455g. Capped them. Take Pic 2.
16:11 Compare this experiment 1A, 2C, 3B and 4C with the data that experiment 178. The same flasks that researcher used. Marked as 1D,2D,3D and 4D

start to measure another solution which have concentrations of 1.3,1.4 and 1.5 [SJK: I don't know what "tube one" means below, especially since the procedure isn't very detailed. It would seem like the log is copies from one line to the next and then editied, so maybe it's supposed to say "tube two" etc.? Not sure.]
16:51 Start to measure 1.3M in tube one. Put the solution into 10ml flask. However, the solution is not enough for 10ml, start to use 5ml. Take Pic 3.
16:57 Start to measure 1.3M in tube one. Put the solution into 5ml flask and measure the total mass which is 10.5334g.
17:03 Start to measure 1.3M in tube one. Put the solution into 2ml flask and measure the total mass which is 7.0750g.
17:06 Start to measure 1.3M in tube one. Put the solution into 1ml flask and measure the total mass which is 18.4110g.
17:09 Start to measure 1.4M in tube two. Put the solution into 5ml flask and measure the total mass which is 10.5293g.
17:13 Start to measure 1.4M in tube two. Put the solution into 2ml flask and measure the total mass which is 7.0883g.
17:14 Start to measure 1.4M in tube two. Put the solution into 1ml flask and measure the total mass which is 10.5334g.
17:16 Start to measure 1.5M in tube three. Put the solution into 5ml flask and measure the total mass which is 10.5422g.
17:20 Start to measure 1.5M in tube three. Put the solution into 2ml flask and measure the total mass which is 7.0811g.
17:23 Start to measure 1.5M in tube three. Put the solution into 1ml flask and measure the total mass which is 18.4340g.