Solving Solubility of Unknown Compound in Base

[HyeLim]

In my lab, I'm trying to identify an unknown compound. So I did a solubility test of the unknown into 5% NaOH. According to the manual it said that if it appears insoluble,take the supernatant out and add 5% HCl until neutral. If percipitate or turbidity results, it means the unknown is an acid.
So far I thought this:
HA (unknown) + OH- <-> H20 + A-
I'm assuming the conjugate base was in the supernatant, but I'm not sure.
A- + HCl <-> Cl- + HA
I'm not sure where the percipitate or turbidity is from. Please help me!

 

[symbolipoint]

In the first part, the organic acid present dissolved (why you obtained the very soluble A anion). Later, you added H+ which recombined with the A- giving you back the fairly insoluble organic acid again, the HA. The HA causes this turbidity or precipitation.

 

[Blueshift5]

Based on the information provided, it seems that you have followed the correct steps to determine the solubility of the unknown compound in base. The precipitate or turbidity that resulted after adding HCl is most likely due to the formation of a new compound, which is the result of a neutralization reaction between the base and the acid form of the unknown compound. This indicates that the unknown compound is indeed an acid.

To further identify the unknown compound, you can perform additional tests such as pH testing, melting point determination, or spectroscopic analysis. These tests can help you narrow down the potential identity of the compound and confirm your initial findings.

Overall, it seems that you have conducted the solubility test correctly and have obtained valuable information about the unknown compound. Keep up the good work and continue to use a systematic approach in your lab experiments.