Question

In an experiment to study the properties of acetic acid, a student takes about 2 mL of acetic acid in a dry test tube. He adds about 2 mL of water to it and shakes the test tube well. He is likely to observe that.

• A. the acetic acid dissolves readily in water
• B. the solution becomes light orange
• C. water floats over the surface of acetic acid
• D. acetic acid floats over the surface of water

Answer 1

The correct option is A

the acetic acid dissolves readily in water

Explanation of correct option:-

Option (A): the acetic acid dissolves readily in water

• There is the presence of $-\mathrm{COOH}$ group in acetic acid (${\mathrm{CH}}_3\mathrm{COOH}$).
• $-\mathrm{COOH}$ group form hydrogen bond with water.
• The hydrogen bond is a weak bond between two molecules that are formed because of the electrostatic attraction between a proton in one molecule and an electronegative atom in another one.
• This will result in the dissolution of acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$ in water.

$\underset{\mathrm{Acetic}\mathrm{acid}}{{\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Hydronium}\mathrm{ion}}{{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Acetate}\mathrm{ion}}{{\mathrm{CH}}_3{\mathrm{COO}}^{-}\left(\mathrm{aq}\right)}$

Explanation of incorrect options:-

Option (B):- the solution becomes light orange

• Acetic acid$\left({\mathrm{CH}}_3\mathrm{COOH}\right)$ is a colorless liquid.
• So, on getting dissolved in water, there won't be any color change in the solution.

Option (C):- water floats over the surface of acetic acid

• The density of water is less than acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$.
• So, on adding acid there would be an exothermic reaction in the container and water won't float over the surface of acetic acid.

Option (D):- acetic acid floats over the surface of the water

• Because the density of water is less than acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$.
• On adding, acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$ will sink in.

Therefore, the correct option is (A):- the acetic acid dissolves readily in water.