Question 1

Which of the following statements best explains why water is used as the first solvent in the solubility test for organic compounds?

Accepted Answer

Water is highly polar, so its use helps to quickly identify compounds with polar functional groups, such as acids, bases, and alcohols.

Question 2

During a solubility test, a student observes that an unknown sample is soluble in 5% NaOH but insoluble in water. What does this result most likely indicate about the functional group present?

Accepted Answer

The compound contains a carboxylic acid group.

Question 3

Which equation correctly represents the reaction of a carboxylic acid with sodium hydroxide during a solubility test?

Accepted Answer

$\mathrm{RCOOH} + \mathrm{NaOH} \rightarrow \mathrm{RCOONa} + \mathrm{H_2O}$

Question 4

A student tests an unknown compound and finds it is soluble in 5% HCl but insoluble in water. Which functional group is most likely present?

Accepted Answer

Amines

Question 5

Which of the following best describes the role of intermolecular forces in the solubility of organic compounds in water?

Accepted Answer

Hydrogen bonding and dipole-dipole interactions between solute and solvent molecules increase solubility in water.

Question 6

Which observation indicates that a compound is insoluble in water during the solubility test?

Accepted Answer

Presence of a precipitate or two distinct layers.

Question 7

Why is it important to use only a small amount of sample and solvent in solubility tests?

Accepted Answer

To minimize waste and reduce exposure to potentially hazardous chemicals.

Question 8

Which of the following compounds would you expect to be soluble in 5% NaOH but not in 5% HCl?

Accepted Answer

Benzoic acid ($\mathrm{C_6H_5COOH}$)

Question 9

A student adds 5% H$_2$SO$_4$ to an unknown sample and observes no change. What does this suggest about the sample?

Accepted Answer

The sample is likely neutral and does not react with strong acids.

Question 10

Which of the following is a correct safety precaution when handling concentrated acids and bases during solubility tests?

Accepted Answer

Wear gloves and goggles, and handle acids and bases in a fume hood.

Question 11

Which of the following best explains why carboxylic acids are soluble in aqueous NaOH but not in water?

Accepted Answer

Carboxylic acids form ionic salts with NaOH, increasing their solubility.

Question 12

Which functional group is most likely present if a compound is soluble in both water and 5% NaOH?

Accepted Answer

Carboxylic acid

Question 13

A student tests an unknown sample and finds it is insoluble in water, NaOH, and HCl. Which of the following is the most likely identity of the sample?

Accepted Answer

Cyclohexane

Question 14

Which of the following equations represents the reaction of an amine with hydrochloric acid?

Accepted Answer

$\mathrm{RNH_2} + \mathrm{HCl} \rightarrow \mathrm{RNH_3^+Cl^-}$

Question 15

Which of the following is NOT a valid reason for performing a solubility test in organic qualitative analysis?

Accepted Answer

To determine the melting point of the compound.

Question 16

A student observes that a sample is soluble in water and forms a homogeneous solution. What additional test should be performed to further identify the functional group?

Accepted Answer

Test solubility in 5% NaOH and 5% HCl.

Question 17

Which of the following best describes the solubility behavior of phenol in the solubility test?

Accepted Answer

Phenol is insoluble in water but soluble in NaOH due to its weakly acidic nature.

Question 18

Which of the following is a correct conclusion if a compound is insoluble in water, NaOH, and HCl, but soluble in ethanol?

Accepted Answer

The compound is likely nonpolar and lacks acidic or basic functional groups.

Question 19

Which of the following is a correct safety procedure if a student accidentally spills concentrated H$_2$SO$_4$ on their skin during the experiment?

Accepted Answer

Immediately rinse the affected area with copious amounts of water and seek medical attention.

EXP 6: Solubility Test for Organic Compounds

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