Chapter 18.1, Problem 5SSC

Interpretation Introduction

Interpretation:

The reason for many Lewis acids and bases to be not classified as Arrhenius or Bronsted-Lowry acids and bases needs to be explained.

Concept introduction:

According to Lewis concept,

Acid is a substance which is electron acceptor and base is a substance which is electron donor.

According to Arrhenius,

Acid is a substance which gives hydrogen ion and Base is a substance which gives hydroxyl ions in aqueous solution.

According to Bronsted-Lowry,

Acid is a substance which donate hydrogen ion and Base is a substance which accept hydrogen ion.

Answer to Problem 5SSC

Many Lewis acids can’t give hydrogen ion that’s why they can‘t classified as Arrhenius or Bronsted-Lowry acids.

Similarly, Lewis bases can’t give hydroxyl ion that’s why they can‘t classified as Arrhenius bases.

However all Lewis bases are Bronsted bases.

Explanation of Solution

Let’s take example to understand:

$AlC{l}_3$is a Lewis acid as it is electron deficient and accepts electron from donor species. But it can’t give $H^{+}$. Therefore, it is not Arrhenius or Bronsted-Lowry acid.

$N{H}_3$ is a Lewis base as it donates electron pair but it can’t classified as Arrhenius base because it can’t donate hydroxyl ion.

But it can accept $H^{+}$ to form $N{H}_4{}^{+}$, so it can be classified as bronsted base.

Conclusion

Thus, Many Lewis acids can’t classify as Arrhenius or Bronsted-Lowry acids.

Many Lewis bases can’t classify as Arrhenius bases.

All Lewis bases are Bronsted bases.