Ammonia is a weak base. If Ammonium nitrate is added to it, the pH of the ammonia solution will _____________ (increase, decrease, stay the same)
Can you use the Henderson-Hasselbalch equation to decide?
pH = pKa + log [(base)/(acid)]
pKa for NH3 is about 4.74.
Calculate the pH of a 0.1 M solution of NH3, then add 0.1 mol NH4NO3 and see which way it goes.
To determine the effect of adding ammonium nitrate to an ammonia solution on its pH, we need to understand the properties of the components involved.
Ammonia (NH3) is indeed a weak base, meaning it partially dissociates in water to produce hydroxide ions (OH-) and ammonium ions (NH4+). The equilibrium reaction is as follows:
NH3 + H2O ⇌ NH4+ + OH-
Ammonium nitrate (NH4NO3) is a salt that completely dissociates in water to produce ammonium ions (NH4+) and nitrate ions (NO3-).
When ammonium nitrate is added to an ammonia solution, the ammonium ions (NH4+) from the salt will react with any hydroxide ions (OH-) produced by the ammonia. This reaction results in the formation of water (H2O) and the regeneration of ammonia:
NH4+ + OH- → NH3 + H2O
Since the hydroxide ions (OH-) are consumed in this reaction, the concentration of hydroxide ions in the solution will decrease. pH is a measure of the concentration of hydrogen ions (H+) in a solution, which is primarily determined by the concentration of hydroxide ions (OH-).
Therefore, when ammonium nitrate is added to an ammonia solution, the reaction between ammonium ions (NH4+) and hydroxide ions (OH-) will decrease the concentration of hydroxide ions, thereby increasing the concentration of hydrogen ions (H+). As a result, the pH of the ammonia solution will decrease, making it more acidic.
In summary, adding ammonium nitrate to an ammonia solution will decrease the pH of the ammonia solution.