Question

Consider 0.10 M solutions of acetic acid, ammonia, hydrochloric acid, and sodium hydroxide. Rank these solutions in order of increasing pH (starting from the lowest, and ending with the highest pH value). Please also make a statement, whether each solution is an acidic or a basic one, and provide an explanation why.

Answer 1

Answer:

HCl < CH₃COOH < NH₃ < NaOH

Explanation:

Given compounds:

Acetic acid: CH₃COOH

Ammonia; NH₃

Hydrochloric acid: HCl

Sodium hydroxide: NaOH

All the solutions are of the same molarity which is 0.1M. We need to see how these compounds dissociate to form solutions in order to establish their pH value:

For Acetic acid;

            CH₃COOH + H₂O ⇄ H₃O⁺ + CH₃COO⁻

   Acetic acid is a weak acid and it ionizes slightly in solutions. It would have a pH close to 7

For Ammonia;

       NH₃ + H₂O ⇄ NH₄⁺ + OH⁻

   Ammonia is a weak base and it ionizes slightly in solutions. It sets up an equilibrium in the process. It's would be slightly above 7

For HCl:

               HCl + H₂O → H₃O⁺ + Cl⁻

HCl is a strong acid and ionizes completely in solutions. It has a very low pH

For NaOH:

          NaOH → Na⁺ + OH⁻

  NaOH ionizes also completely in solutions and it breaks down into sodium and hydroxide ions. It is a strong base and it would have a high PH value.

                 HCl < CH₃COOH < NH₃ < NaOH

This is the trend of increasing pH