To solve this problem, we'll need to identify the species acting as acids, bases, and their corresponding conjugate pairs in the reaction:
[tex]\[ H_2 PO_4^{-} + H_2 O \rightleftharpoons HPO_4^{2-} + H_3 O^{+} \][/tex]
Here's a step-by-step solution to identify the conjugate acid-base pairs:
1. Identify the Acid and Its Conjugate Base:
- An acid donates a proton (H⁺).
- In the reaction, dihydrogen phosphate ([tex]\( H_2 PO_4^{-} \)[/tex]) donates a proton to water, becoming hydrogen phosphate ([tex]\( HPO_4^{2-} \)[/tex]).
- Therefore, [tex]\( H_2 PO_4^{-} \)[/tex] is the acid and [tex]\( HPO_4^{2-} \)[/tex] is its conjugate base.
2. Identify the Base and Its Conjugate Acid:
- A base accepts a proton (H⁺).
- Water ([tex]\( H_2 O \)[/tex]) accepts a proton from dihydrogen phosphate, becoming a hydronium ion ([tex]\( H_3 O^{+} \)[/tex]).
- Therefore, [tex]\( H_2 O \)[/tex] is the base and [tex]\( H_3 O^{+} \)[/tex] is its conjugate acid.
Now we can classify each of the species into the appropriate categories:
- Acid: [tex]\( H_2 PO_4^{-} \)[/tex]
- Conjugate Base: [tex]\( HPO_4^{2-} \)[/tex]
- Base: [tex]\( H_2 O \)[/tex]
- Conjugate Acid: [tex]\( H_3 O^{+} \)[/tex]
Thus, the correct identification and placement for the conjugate acid-base pairs are:
- Acid:
- [tex]\( H_2 PO_4^{-} \)[/tex]
- Conjugate Base:
- [tex]\( HPO_4^{2-} \)[/tex]
- Base:
- [tex]\( H_2 O \)[/tex]
- Conjugate Acid:
- [tex]\( H_3 O^{+} \)[/tex]
