based on the qualitative organic analysis

1. Why is it important to have clean test tubes before running a test?
Before which tests should acetone not be used to clean the test tubes?

2. Why run solubility tests before running the functional group classification tests?
Solubility tests helps to determine the size and polarity of an unknown compound and the presence of basic or acidic functional groups. Knowledge of the acidity of the functional group helps to narrow down the functional group of a substance during the classification tests.

3. Determine the functional group present in these unknown:
(a) Unknown A is soluble in water and gives bubbles with5% NaHCO3. – carboxylic acid
(b) Unknown B is insoluble in water, insoluble in 5% NaOH, but soluble in 5% HCl.
(c) Unknown C is insoluble in water, insoluble in 5% NaOH, insoluble in 5% HCl, soluble with a color change in conc. H2SO4, and decolorizes both KMnO4 (aq) and bromine in cyclohexane.
(d) Unknown D is soluble in water, does not produce bubbles with 5% NaHCO3, gives a precipitate with 2,4-DNP, and gives a hsia color with the Schiff test.

4. In each of the following cases, describe the next test you would perform.
(a) Unknown X is insoluble in water, 5% NaOH, 5% HCl, and conc. H2SO4.
(b) Unknown Y is insoluble in water, soluble in 5% NaOH, and insoluble in 5% NaHCO3.
(c) Unknown Z is insoluble in water, insoluble in 5% NaOH, insoluble in 5% HCl, and soluble in conc. H2SO4.

5. You suspect that your unknown contains halogen, so you perform the silver nitrate in ethanol test and the sodium iodide in acetone test, both of which are negative. Do these results prove that your compound does not contain a halogen? Briefly explain.