Unnati Hajari


To determine the solubility of trans-cinnamic acid in methanol using the density method .


Two 20mL test tubes with stoppers or screw tops.
250mL beaker
Hot Plate
A 5mL,2mL, and 1mL Volumetric flask
Weighing scale
Weighing paper
Trans-Cinnamic acid
Graduated Cylinder


Dissolve cinnamic acid in 40C-45C water bath. Wait 7-10 minutes until cinnamic acid has dissolved and created a saturated solution. Remove the supernatant and place in a 25C water bath and let a precipitate form. Weigh 5mL of the supernatant using a 5mL volumetric flask. Then weigh 2mL of the supernatant using a 2mL volumetric flask and then weigh 1mL of the supernatant using a 1mL volumetric flask. Weigh three times in different volumes to compare molarity variations.


Calculation Sheet 1
The molarity when 5mL of the supernatant was weighed was 1.226M. The molarity when 2mL of the supernatant was weighed was 1.169M. The molarity when 1mL of the supernatant was weighed was 1.376M.


[compare your results with previous reports JCB]


Using the density method I found that solubility of cinnamic acid in methanol is approximately 1.257M at 26C. I achieved the molarity by taking the average of the molarity of the 5mL, 2mL, and 1mL solutions.(((1.226M+1.169M+1.376M)/3)=1.257M)



11:46 - Weighed out 4.9g of cinnamic acid. Using a funnel, the 4.9g of the acid was transferred to a 20mL test tube.
11:55 - Started heating approximately 200 mL of water at 200C. Initial temperature was 24C.
12:02 - 10mL of methanol was measured using a graduated cylinder.
12:09 - 10mL of methanol was added to the 4.9g of cinnamic acid. place in water bath when temperature was 43C. Now heating at 5C because temperature was rising too fast.
12:14 - Temperature is at 41C.
12:18 - Temperature is 40 C.
12:21 - Since the water level was only covering the solids in the test tube I added approximately 125mL-150mL additional water. Temperature is at 34C, so I increased temperature to 200C.
12.25 - Temperature is 40C.
12:28 - 44C Reduced temperature to 100C so the temperature of the water bath stays between 40C-45C.
12:31 - Inverted 4 times.
12:35 - Took the test tube out of the water bath. Temperature is at 46C.
12:38 - Transfered the supernatant into another 20mL test tube.
12:40 - Put the 20mL test tube of the supernatant into a 26C (try to make it 25C) water bath.
12:44 - Precipitate appears. Temperature of water bath is still 26C.
12:45 - Inverted a few times.
(Left to go to class)
14:03 - temperature is approximately 24.5C.
14:13 - Weighed the 5 mL volumetric flask = 23.7958g
14:17 - 5mL of Pure methanol in the 5mL volumetric flask weighed 27.7629g.
14:19 - Pour out the methanol and dry properly and add 5mL of the supernatant, using a pipet.
14:22 - The 5mL of supernatant and flask weighed 28.0933g.
14:25 - The 2mL flask that was empty was weighed= 14.6372g.
14:26 - Transferred 2mL of the supernatant.
14:27 - Weighed the 2mL of supernatant = 16.3902. Weighed an empty 1mL volumetric flask= 42.8280g.
14:28 - Transferred and weighed the 1mL of the supernatant= 43.6736g.
(14:25-14:28 was done incorrectly because I did not weight the 2mL and 1mL flasks with pure methanol, so I did it again)
14:43 - The 2mL flask that was empty was weighed=14.6385g.
14:43 - 2mL of pure methanol was transferred into the 2mL flask with a pipette.
14:44 - 2mL of pure methanol + the flask weighed= 16.2224g. The flask was then dried completely.
14:47 - Transferred 2mL of the supernatant.
14:48 - The 2mL of supernatant + the flask weighed= 16.3551g. Weighed an empty 1mL volumetric flask=37.3024g.
14:49 - 1mL of pure methanol was added.
14:50 - The 1mL of pure methanol + the flask weighed= 38.0973g. The flask was then completely dried.
14:51 - 1mL of the supernatant was added. Since I did not have much supernatant left in the 20mL test tube, I used 1mL from the 5mL flask.
14:52 - The 1mL of the supernatant + the flask weighed= 38.1712g.