Q.10.11 - An Introduction to General, Organic, and Biological Chemistry

Question

Write the formula for the conjugate acid for each of the following bases:

a. CO₃^2-

b. ${\mathrm{H}}_2\mathrm{O}$

c. ${\mathrm{H}}_2{{\mathrm{PO}}_4}^{-}$

d. ${\mathrm{Br}}^{-}$

Step-by-Step Solution

Answer

a. The formula of the conjugate acid is ${{\mathrm{HCO}}_3}^{-}$.

b. The formula of the conjugate acid is ${\mathrm{H}}_3{\mathrm{O}}^{+}$.

c. The formula of the conjugate acid is ${\mathrm{H}}_3{\mathrm{PO}}_4$.

d.  The formula of the conjugate acid is $\mathrm{HBr}$.

Step 1: Part (a) Given information

To write the conjugate acid of CO₃^2- .

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 base is CO₃^2- , thus its conjugate acid can be represented as:

${{\mathrm{CO}}_3}^{2-}\left(\mathrm{aq}\right)+{\mathrm{H}}^{+}\left(\mathrm{aq}\right)\rightleftharpoons {{\mathrm{HCO}}_3}^{-}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

Therefore, the conjugate acid for the given base is ${{\mathrm{HCO}}_3}^{-}$.

Step 1: Part (b) Given information

To write the conjugate acid of ${\mathrm{H}}_2\mathrm{O}$.

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 base is ${\mathrm{H}}_2\mathrm{O}$ , thus its conjugate acid can be represented as:

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

Therefore, the conjugate acid for the given base is ${\mathrm{H}}_3{\mathrm{O}}^{+}$.

Step 1: Part (c) Given information

To write the conjugate acid of ${\mathrm{H}}_2{{\mathrm{PO}}_4}^{-}$.

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 base is ${\mathrm{H}}_2{{\mathrm{PO}}_4}^{-}$ , thus its conjugate acid can be represented as:

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

Therefore, the conjugate acid for the given base is ${\mathrm{H}}_3{\mathrm{PO}}_4$.

Step 1: Part (d) Given information

To write the conjugate acid of ${\mathrm{Br}}^{-}$.

Step 2: Part (d) 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 base is ${\mathrm{Br}}^{-}$ , thus its conjugate acid can be represented as:

${\mathrm{Br}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons \mathrm{HBr}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

Therefore, the conjugate acid for the given base is $\mathrm{HBr}$.