Final answer:
The acid in this reaction is H3PO4, and its conjugate base is H₂PO4. The base is NH3, and its conjugate acid is NH4+. The patterns in the periodic table explain why these substances act as acids and bases.
Step-by-step explanation:
In this reaction, H3PO4 is the acid that donates a proton, and its conjugate base is H₂PO4. NH3 is the base that accepts a proton, and its conjugate acid is NH4+. The patterns in the periodic table can explain why these substances act as acids and bases. H3PO4 is a stronger acid than H₂PO4 because the electronegativity of oxygen in H3PO4 is higher than in H₂PO4. This makes it easier for H₃PO₄ to donate a proton. Similarly, NH4+ is a stronger acid than NH3 because the electronegativity of the hydrogen in NH4+ is higher than in NH3, making it easier for NH4+ to donate a proton.