Statement 1 p-Nitrophenol is a stronger acid than o-Nitrophenol. and Statement 2 Steric effect due to the presence of \(-\mathrm{NO}_{2}\) group at ortho position of -OH group decreases the acidic strength of oNitrophenol.

In organic chemistry, resonance structures play a crucial role in determining the stability and reactivity of molecules. For compounds like nitrophenols, which can donate a hydrogen ion, becoming an anion, the stability of this anion—or conjugate base—is highly relevant to the molecule's acidic strength.

Resonance involves the delocalization of electrons, which essentially means that electrons can be spread out over several atoms, distributing the charge and thus stabilizing the molecule. If we take the example of p-Nitrophenol, once the hydrogen ion is donated, the resulting negative charge on the oxygen can be spread out over the molecule through the nitro group. This delocalization is depicted in resonance structures, which are various forms that the molecule can theoretically take.

Each resonance structure contributes to the overall stability of the conjugate base because the negative charge is not localized on a single oxygen atom but rather is shared across several atoms. It's like sharing the weight of a heavy backpack—spreading the weight (or in this case, the negative charge) makes it easier to carry (or more stable for the molecule). This ability to share the negative charge across multiple atoms makes p-Nitrophenol a stronger acid compared to o-Nitrophenol, which due to its structure, cannot delocalize the charge as effectively.

When we discuss steric effects, we are looking at the impact of the physical size and spatial orientation of atoms or groups within a molecule on its properties and reactions. This is pertinent to understanding why o-Nitrophenol is less acidic than p-Nitrophenol.

In o-Nitrophenol, the nitro group ({-NO_2}) is attached at the ortho position, which is directly adjacent to the hydroxyl group ({-OH}). This close proximity creates a crowded environment—an effect known as steric hindrance. The bulkiness of the nitro group clashes with the hydroxyl group, making it less likely for the hydrogen ion to detach because the groups cannot move freely.

The steric crowding can also inhibit the necessary molecular reorganization that would allow for the effective delocalization of the negative charge post ionization. It's akin to trying to move through a densely packed crowd—it's much more difficult than if the crowd were spread out. This decrease in effective interaction due to steric hindrance inherently decreases o-Nitrophenol's ability to act as an acid.

The final piece of the puzzle in understanding the acidic strength of nitrophenols lies in the concept of conjugate base stability. A conjugate base is the species that remains after an acid has donated a hydrogen ion (H+). The stability of this conjugate base directly impacts the willingness of the acid to release the hydrogen ion in the first place—the more stable the base, the stronger the acid.

After the loss of a hydrogen ion, the negatively charged oxygen left behind on the nitrophenol needs to be stabilized. Resonance structures, as discussed earlier, are a key factor in this stabilization. However, the stability of the conjugate base isn't determined by resonance alone.

The overall molecular structure, including factors like polarity, inductive effects, and yes, the aforementioned steric effects, all interplay to either shore up or undermine the stability of the conjugate base. In the case of nitrophenols, p-Nitrophenol exhibits greater conjugate base stability due to its ability to utilize resonance structures effectively and lack of steric hindrance. Conversely, o-Nitrophenol, hampered by steric effects and fewer resonance possibilities, translates to a less stable conjugate base, thus making it a weaker acid.