Q.10.13 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify the Bronsted-Lowry Acid-Base pair in each of the following equations.

a. ${\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {{\mathrm{HCO}}_3}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)$

b. ${{\mathrm{NH}}_4}^{+}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {\mathrm{NH}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)$

c. $\mathrm{HCN}\left(\mathrm{aq}\right)+{{\mathrm{NO}}_2}^{-}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{CN}}^{-}\left(\mathrm{aq}\right)+{{\mathrm{HNO}}_2}^{-}\left(\mathrm{aq}\right)$

Step-by-Step Solution

Answer

a. The conjugate acid-base pair are ${\mathrm{H}}_2{\mathrm{CO}}_3/{{\mathrm{HCO}}_3}^{-}$ and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}_3{\mathrm{O}}^{+}$.

b. The conjugate acid-base pair are ${{\mathrm{NH}}_4}^{+}/{\mathrm{NH}}_3$ and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}_3{\mathrm{O}}^{+}$.

c. The conjugate acid-base pair are $\mathrm{HCN}/{\mathrm{CN}}^{-}$ and ${{\mathrm{NO}}_2}^{-}/{{\mathrm{HNO}}_2}^{-}$.

Step 1: Part (a) Given information

The given equation is ${\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {{\mathrm{HCO}}_3}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)$.

Step 2: Part (a) Explanation

As per Bronsted Lowry, conjugate acid-base pairs are comprised of molecules or ions that are related to the loss of a proton.

A conjugate base pair is present in every acid-base reaction. It can be seen that when an acid reacts with a base it produces a conjugate acid and a conjugate base.

The given chemical equation is as follows:

${\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {{\mathrm{HCO}}_3}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)$

Therefore, the conjugate acid-base pairs are ${\mathrm{H}}_2{\mathrm{CO}}_3/{{\mathrm{HCO}}_3}^{-}$and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}_3{\mathrm{O}}^{+}$.

Step 1: Part (b) Given information

The given chemical equation is ${{\mathrm{NH}}_4}^{+}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {\mathrm{NH}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)$.

Step 2: Part (b) Explanation

As per Bronsted Lowry, conjugate acid-base pairs are comprised of molecules or ions that are related to the loss of a proton.

A conjugate base pair is present in every acid-base reaction. It can be seen that when an acid reacts with a base it produces a conjugate acid and a conjugate base.

The given chemical equation is as follows:

${{\mathrm{NH}}_4}^{+}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {\mathrm{NH}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)$

Therefore, the conjugate acid-base pairs are ${{\mathrm{NH}}_4}^{+}/{\mathrm{NH}}_3$and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}_3{\mathrm{O}}^{+}$.

Step 1: Part (c) Given information

The given chemical equation is $\mathrm{HCN}\left(\mathrm{aq}\right)+{{\mathrm{NO}}_2}^{-}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{CN}}^{-}\left(\mathrm{aq}\right)+{{\mathrm{HNO}}_2}^{-}\left(\mathrm{aq}\right)$.

Step 2: Part (c) Explanation

As per Bronsted Lowry, conjugate acid-base pairs are comprised of molecules or ions that are related to the loss of a proton.

A conjugate base pair is present in every acid-base reaction. It can be seen that when an acid reacts with a base it produces a conjugate acid and a conjugate base.

The given chemical equation is as follows:

$\mathrm{HCN}\left(\mathrm{aq}\right)+{{\mathrm{NO}}_2}^{-}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{CN}}^{-}\left(\mathrm{aq}\right)+{{\mathrm{HNO}}_2}^{-}\left(\mathrm{aq}\right)$

Therefore, the conjugate acid-base pairs are $\mathrm{HCN}/{\mathrm{CN}}^{-}$and ${{\mathrm{NO}}_2}^{-}/{{\mathrm{HNO}}_2}^{-}$