Q.10.101 - An Introduction to General, Organic, and Biological Chemistry

Question

For each of the following: (10.2,10.3)

1. $H_{2}S$   2.$H_{3}P{O}_4$

a. Write the formula for the conjugate base.

b. Which is the weaker acid?

Step-by-Step Solution

Answer

Part (a) . For $H_{2}S$- $H{S}^{-}$ and for $H_{3}P{O}_4$-$H_{2}P{O_4}^{-}$

Part (b) . $H_{2}S$ is weaker

Step 1: Information Part (a)

A conjugate acid-base pair comprises two substances that vary exclusively by the presence of a proton (H⁺). 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 base is shaped when a proton is eliminated from an acid.

Hence,

The conjugate base of $H_{2}S$ is $H{S}^{-}$due to the loss of one $H^{+}$ion.

The conjugate base of ${\mathrm{H}}_3{\mathrm{PO}}_4\text{ is }{\mathrm{H}}_2{\mathrm{PO}}_4^{-}$due to the loss of one $H^{+}$ion.

Step 3: Explanation Part (b)

A stronger conjugate base means a weak acid. 

Thus,

$H_{2}S$ is the weaker acid as $H{S}^{-}$ is a stronger conjugate base than $H_{2}P{O_4}^{-}$.