Recrystalization and Melting Points lab Ended up with no crop B... weight of cro
ID: 892066 • Letter: R
Question
Recrystalization and Melting Points lab
Ended up with no crop B...
weight of crop A started with- 0.3g
crop A after recrystalization: 0.3448
(40 Points)
a. How different is the solubility of salicylic acid and adipid acid in water?
b. In your procedure you are asked to bring your dissolved mixture to room temperature and collect a solid before you drop the remaining liquid temperature to 0oC. Knowing you have a mixture of compounds with different solubility, why do you think it was done? what would happen if the whole dissolved compounds were put in an ice bath at 0oC?
c. Without looking into your MP results yet, and based on table for MP/identity of crop A&B, what is the identity (expected) for crop A and crop B?
d. How do your measurements of MP support the identification of Crop A and Crop B?
e. What does your MP measurements tell you about the purity of your Crop A and Crop B?
f. Calculate the recover yield for your recrystallization (Crop A and Crop B)
g. what does the recover yield tell you about the loss of your compounds?
h. What are the general sources of loss of your compounds in this experiment? Describe how/where you believe your losses happened and how to improve the loss in future experiments
crop MP crop mixed MP with salicylic acid mixed MP with adipic acid identity of crop A 157-160 158-161 145-149 salicylic acid B -- --- --- ---Explanation / Answer
a) In water, the solubility of salicylic acid is 2 g/L at 293 K and the solubility of adipic acid 24 g/L at 298 K.
Thus, adipic acid is much more water soluble than salicylic acid.
b) When the mixture is brought to room temperature, the more soluble compound (salicylic acid) will remain soluble and the less soluble compound (adipic acid) will crystallize out.
If the whole dissolved compounds were put in an ice bath, no separation will occur and both salicylic acid and adipic acid will crystallize out simultaneously.
c). Crop A is obtained at room temperature. It should be less soluble salicylic acid.
Crop B should be obtained at 0 deg C and it should be adipic acid.
d) The melting point of crop A is in the range 157-160. It is the same range 158-161 of salicylic acid. The melting range of adipic acid is 145-149. It is much lower than the melting range of crop A.
Hence, the crop A is salicylic acid.
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