Q.10.104 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify the conjugate acid-base pairs in each of the following equations:

a. ${\mathrm{HNO}}_2\left(aq\right)+{\mathrm{HS}}^{-}\left(aq\right)\rightleftarrows {\mathrm{NO}}_2^{-}\left(aq\right)+{\mathrm{H}}_2\mathrm{S}\left(g\right)$

b. $\mathrm{HCl}\left(aq\right)+{\mathrm{OH}}^{-}\left(aq\right)⟶{\mathrm{Cl}}^{-}\left(aq\right)+{\mathrm{H}}_2\mathrm{O}\left(l\right)$

Step-by-Step Solution

Answer

Part (a) . ${\mathrm{HS}}^{-}\left(aq\right)\to {\mathrm{H}}_2\mathrm{S}\left(aq\right)$ and $\mathrm{HCl}\left(aq\right)\to {\mathrm{Cl}}^{-}\left(aq\right)$

Part (b) . ${\mathrm{H}}_2\mathrm{O}\left(l\right)\to {\mathrm{OH}}^{-}\left(aq\right)$ and ${\mathrm{HNO}}_2\left(aq\right)\to {\mathrm{NO}}_2^{-}\left(aq\right)$

Step 1: Given Information (Part a)

In the Brønsted-Lowry meaning of acids and bases, a conjugate acid-base pair comprises two substances that vary exclusively by the presence of a proton. A conjugate acid is framed when a proton is added to a base, and a conjugate base is shaped when a proton is eliminated from an acid.

Step 2: Explanation Part (a)

A conjugate acid is framed when a proton is added to a base, and a conjugate base is shaped when a proton is eliminated from an acid. 

Hence,

the conjugate acid-base pairs are,

${\mathrm{HS}}^{-}\left(aq\right)\to {\mathrm{H}}_2\mathrm{S}\left(aq\right)$ and $\mathrm{HCl}\left(aq\right)\to {\mathrm{Cl}}^{-}\left(aq\right)$

Step 3: Explanation Part (b)

A conjugate acid is framed when a proton is added to a base, and a conjugate base is shaped when a proton is eliminated from an acid. 

Hence,

the conjugate acid-base pairs are,

${\mathrm{H}}_2\mathrm{O}\left(l\right)\to {\mathrm{OH}}^{-}\left(aq\right)$ and ${\mathrm{HNO}}_2\left(aq\right)\to {\mathrm{NO}}_2^{-}\left(aq\right)$