Question

Consider this reaction: H3BO3(aq) + HS-(aq) H2BO3-(aq) + H2S(aq) What is the sequence of Brønsted-Lowry acids and bases? A.base + acid acid + base B.acid + base acid + base C.acid + base base + acid D.base + acid base + acid

Answer 1

Answer: The correct answer is Option C.

Explanation:

According to the Bronsted-Lowry conjugate acid-base theory, an acid is defined as a substance which looses protons and thus forming conjugate base and a base is defined as a substance which accepts protons and thus forming conjugate acid.

For the given chemical equation:

$H_3BO_3(aq.)+HS^-(aq.)\rightarrow H_2BO_3^-(aq.)+H_2S(aq.)$

Here, $H_3BO_3$ is loosing a proton, thus it is considered as an acid and after losing a proton, it forms $H_2BO_3^-$ which is a conjugate base.

And, $HS^-$ is gaining a proton, thus it is considered as a base and after gaining a proton, it forms $H_2S$ which is a conjugate acid.

The sequence of the acids and bases in the above equation are:

$Acid+Base\rightarrow Base+Acid$

Hence, the correct answer is Option C.

Answer 2

Answer : The correct option is (C).

Explanation :

According to the Bronsted Lowry concept, Bronsted Lowry-acid is a substance that donates one or more hydrogen ion in a reaction and Bronsted Lowry-base is a substance that accepts one or more hydrogen ion in a reaction.

Or we can say that, conjugate acid is proton donor and conjugate base is proton acceptor.

The given equilibrium reaction will be,

$H_3BO_3(aq)+HS^-(aq)\rightleftharpoons H_2BO_3^-(aq)+H_2S(aq)$

In this reaction, $H_3BO_3$ is an acid that donate a proton or hydrogen to $HS^-$ base and it forms $H_2BO_3^-$ and $H_2S$ are conjugate base and acid respectively.

That means, $H_3BO_3$ and $HS^-$ are acid and base and $H_2BO_3^-$ and $H_2S$ are conjugate base and acid respectively.

The general sequence of Brønsted-Lowry acids and bases is:

$\text{Acid}+\text{Base}\rightleftharpoons \text{Conjugate Base}+\text{Conjugate Acid}$

From the given option we conclude that the correct sequence will be:

$\text{Acid}+\text{Base}\rightleftharpoons \text{Base}+\text{Acid}$

Hence, the correct option is (C) $\text{Acid}+\text{Base}\rightleftharpoons \text{Base}+\text{Acid}$