Which statement correctly describes the solubility of nitrates in water?

• A. No nitrates are soluble in water.
• B. Some nitrates are insoluble in water.
• C. Nitrates react with water to form acids.
• D. All nitrates are soluble in water.

Answer: (D)

Nitrates dissolve in water because nitrate salts are universally soluble. When they dissolve, they separate into ions (the nitrate ion NO3− and the accompanying cation like Na+, K+, or NH4+). Water molecules surround and stabilize both ions very effectively, releasing a lot of energy (hydration energy) and not having strong enough lattice energy to hold the solid together. That combination makes dissolution favorable for all common nitrates.

So statements claiming no nitrates dissolve or that some nitrates are insoluble aren’t accurate, since many nitrate salts readily dissolve. The idea that nitrates react with water to form acids isn’t correct here either: nitrate is the conjugate base of a strong acid (nitric acid) and doesn’t react with water to produce more nitric acid.