Separation Techniques and Chemical Reactions

Which lab technique is used to quickly check the results of tiny chemical reactions before performing a larger-scale experiment?

• Distillation

• Recrystallization

• Thin-layer chromatography (TLC)

• Proton NMR

Why is an old bottle of acetyl chloride, which has been opened many times, likely to be contaminated?

• It reacts with oxygen in the air.

• It reacts with water vapor in the air.

• It loses its color over time.

• It becomes too cold to be effective.

What property of liquids is primarily used to separate them through distillation?

• Density

• Boiling point

• Color

• Magnetic attraction

For a solid to be purified effectively by recrystallization, how should it behave in the chosen solvent?

• It should be insoluble when heated and soluble at room temperature.

• It should be soluble when heated and insoluble or slightly soluble at room temperature.

• It should be soluble at all temperatures.

• It should be insoluble at all temperatures.

What laboratory technique is used to separate pure solid crystals from a liquid mixture by drawing the liquid through a filter using suction?

• Distillation

• Chromatography

• Vacuum filtration

• Evaporation

Which type of chemical group, when already attached to a benzene ring, directs new incoming groups to the ortho or para positions?

• Meta directors

• Electron-withdrawing groups

• Ortho/para directors

• Deactivating groups

To create a para-substituted product like 1-bromo-4-nitrobenzene from benzene, which group should be added to the benzene ring first?

• The nitro group (NO2)

• The bromine atom (Br)

• Both groups simultaneously

• It does not matter which group is added first

If a benzene ring has both a hydroxyl (-OH) group and a sulfonic acid (-SO3H) group, and a new group is added, which existing group will primarily determine where the new group attaches?

• The hydroxyl (-OH) group

• The sulfonic acid (-SO3H) group

• Both groups equally

• Neither group, the new group attaches randomly