Select the correct answer.

Which statement correctly relates two substances in this chemical equation?

[tex]\( NH_3 + H_2O \rightleftharpoons OH^{-} + NH_4^{+} \)[/tex]

A. [tex]\( H_2O \)[/tex] is the conjugate base of [tex]\( OH^{-} \)[/tex].

B. [tex]\( H_2O \)[/tex] is the conjugate acid of [tex]\( NH_3 \)[/tex].

C. [tex]\( NH_4^{+} \)[/tex] is the conjugate acid of [tex]\( NH_3 \)[/tex].

D. [tex]\( NH_3 \)[/tex] is the conjugate acid of [tex]\( NH_4^{+} \)[/tex].

E. [tex]\( OH^{-} \)[/tex] is the conjugate base of [tex]\( NH_3 \)[/tex].



Answer :

To determine the correct statement, let's examine the chemical equation:
[tex]$ NH_3 + H_2O \rightleftharpoons OH^{-} + NH_4^{+} $[/tex]

In this reaction, ammonia ([tex]$NH_3$[/tex]) reacts with water ([tex]$H_2O$[/tex]).

1. Analyze the role of [tex]$NH_3$[/tex]:
- [tex]$NH_3$[/tex] accepts a proton (H[tex]$^{+}$[/tex]) from water ([tex]$H_2O$[/tex]), forming [tex]$NH_4^{+}$[/tex].
- Therefore, [tex]$NH_3$[/tex] acts as a Bronsted-Lowry base.

2. Analyze the role of [tex]$H_2O$[/tex]:
- [tex]$H_2O$[/tex] donates a proton (H[tex]$^{+}$[/tex]) to [tex]$NH_3$[/tex], forming [tex]$OH^{-}$[/tex].
- Thus, [tex]$H_2O$[/tex] acts as a Bronsted-Lowry acid.

3. Identify the conjugate pairs:
- When [tex]$NH_3$[/tex] accepts a proton, it becomes [tex]$NH_4^{+}$[/tex].
- [tex]$NH_4^{+}$[/tex] is the conjugate acid of [tex]$NH_3$[/tex].
- When [tex]$H_2O$[/tex] donates a proton, it becomes [tex]$OH^{-}$[/tex].
- [tex]$OH^{-}$[/tex] is the conjugate base of [tex]$H_2O$[/tex].

Given these relationships, let's review the answer options:

A. [tex]$H_2O$[/tex] is the conjugate base of [tex]$OH^{-}$[/tex].
- This is incorrect. [tex]$H_2O$[/tex] is the conjugate acid of [tex]$OH^{-}$[/tex], not the conjugate base.

B. [tex]$H_2O$[/tex] is the conjugate acid of [tex]$NH_3$[/tex].
- This is incorrect. [tex]$H_2O$[/tex] gives [tex]$OH^{-}$[/tex], [tex]$H_2O$[/tex] and [tex]$NH_3$[/tex] are not related in an acid-base conjugate pair directly.

C. [tex]$NH_4^{+}$[/tex] is the conjugate acid of [tex]$NH_3$[/tex].
- This is correct. [tex]$NH_4^{+}$[/tex] forms when [tex]$NH_3$[/tex] gains a proton, making it the conjugate acid.

D. [tex]$NH_3$[/tex] is the conjugate acid of [tex]$NH_4^{+}$[/tex].
- This is incorrect. [tex]$NH_3$[/tex] is the base form; [tex]$NH_4^{+}$[/tex] is the conjugate acid.

E. [tex]$OH^{-}$[/tex] is the conjugate base of [tex]$NH_3$[/tex].
- This is incorrect. [tex]$OH^{-}$[/tex] is the conjugate base of [tex]$H_2O$[/tex], not [tex]$NH_3$[/tex].

Therefore, the correct statement is:
C. [tex]$NH_4^{+}$[/tex] is the conjugate acid of [tex]$NH_3$[/tex].