Question

4. What is the nature of the aqueous solution of Pb(NO3)2? Justify your answer by labeling the process with a condensed ionic equation. How will the pH of the medium change if the solution is heated,​

Answer 1

Ответ:

The aqueous solution of Pb(NO3)2 is acidic in nature because the nitrate ion (NO3-) is a weak conjugate base of a strong acid (HNO3), which can hydrolyze in water to produce H+ ions.

The ionic equation for the dissociation of Pb(NO3)2 in water is as follows:

Pb(NO3)2 (s) → Pb2+ (aq) + 2NO3- (aq)

In this equation, Pb(NO3)2 dissociates into Pb2+ and NO3- ions when it dissolves in water. These ions can interact with water molecules to produce H+ and OH- ions. However, since Pb2+ ions can react with OH- ions to form an insoluble precipitate of Pb(OH)2, the hydrolysis reaction is shifted towards the formation of H+ ions. Therefore, the aqueous solution of Pb(NO3)2 is acidic.

If the solution is heated, the solubility of Pb(OH)2 will decrease, and the concentration of OH- ions will decrease. This will cause the pH of the medium to decrease, making the solution more acidic.

Answer 2

Pb(NO3)2 is a salt that dissociates completely in water to form ions. The nature of the aqueous solution of Pb(NO3)2 is acidic due to the presence of the nitrate ions (NO3-) which do not hydrolyze and remain neutral, but the lead ions (Pb2+) can hydrolyze and contribute to the acidity.

The hydrolysis of lead ions can be represented by the following equation:

Pb2+ (aq) + 2H2O (l) → Pb(OH)2 (s) + 2H+ (aq)

In this reaction, lead ions react with water to form lead(II) hydroxide (Pb(OH)2) precipitate and release hydrogen ions (H+) into the solution. The presence of hydrogen ions makes the solution acidic.

Now, if the solution is heated, the equilibrium between lead ions and lead(II) hydroxide will shift towards the left to some extent. This is because an increase in temperature generally favors the dissociation of weak acids or hydrolysis reactions. As a result, more lead ions will be formed, leading to an increase in the concentration of hydrogen ions and further increasing the acidity of the solution.

Therefore, heating the solution of Pb(NO3)2 will increase the pH of the medium and make it even more acidic.