Q. 10.7 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify the reactant that is a Brønsted-Lowry acid and the reactant that is a Brønsted-Lowry base in each of the following:

a. $\mathrm{HI}\left(aq\right)+{\mathrm{H}}_2\mathrm{O}\left(l\right)⟶{\mathrm{I}}^{-}\left(aq\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(aq\right)$

b. ${\mathrm{F}}^{-}\left(aq\right)+{\mathrm{H}}_2\mathrm{O}\left(l\right)\rightleftarrows \mathrm{HF}\left(aq\right)+{\mathrm{OH}}^{-}\left(aq\right)$

Step-by-Step Solution

Answer

(Part a) Hl is Bronsted Lowry acid and ${\mathrm{H}}_2\mathrm{O}$ is a Bronsted Lowry base.

(Part b)${\mathrm{F}}^{-}$ is Bronsted Lowry base and  ${\mathrm{H}}_2\mathrm{O}$ is a Bronsted Lowry acid.

Both the reactants are Bronsted Lowry acid and base. 

Step 1- Introduction (part a)

Bronsted-Lowry acid-base system:

Acid:

According to Bronsted Lowry, acids are substances that donate $H^{+}$ (hydrogen ions) or protons. In general, Bronsted-Lowry acid is a proton donor.  

Base:  

According to Bronsted Lowry, a base is a substance that takes $H^{*}$

 (hydrogen ion) or protons. In general, Bronsted Lowry bases are proton acceptors. 

$\mathrm{HF}+{\mathrm{NH}}_3\to {\mathrm{NH}}_4^{+}+{\mathrm{Cl}}^{-}$

Acid base 

Step 2- Information (Part a)

Acid-base neutralization: 

When an acid reacts with a base to form an ionic salt with water or a solvent, the reaction is known as an acid-base neutralization reaction. 

$\mathrm{HCl}\left(aq\right)+\mathrm{KOH}\left(aq\right)\to {\mathrm{H}}_2\mathrm{O}\left(l\right)+\mathrm{KCl}\left(aq\right)$

    Acid          Base              Water        Salt

Step 3- Explanation (part a)

a.

In this reaction, $HI$ is the Bronsted Lowry acid, the substance that provides $H^{+}$ (hydrogen ion) or proto.

$H_2 O$ is a substance that accepts Bronsted Lowry bases, that is, $H^{+}$(hydrogen ions) or protons.

$\mathrm{HI}\left(aq\right)+{\mathrm{H}}_2\mathrm{O}\left(l\right)\to {\mathrm{H}}_3{\mathrm{O}}^{+}\left(aq\right)+{\mathrm{I}}^{-}\left(aq\right)$

       Acid        Base

Step 4- Explanation (part b)

b.

In this reaction, $H_{2}O$ is the Bronsted Lowry acid, which is the substance that provides $H^{+}$ (hydrogen ion) or proto.

$F ¯$ is a substance that accepts Bronsted Lowry bases, that is, $H^{+}$ (hydrogen ions) or protons

${\mathrm{H}}_2\mathrm{O}\left(l\right)+{\mathrm{F}}^{-}\left(aq\right)\to \mathrm{HF}\left(aq\right)+{\mathrm{OH}}^{-}\left(aq\right)$

      Acid        Base