Question

The plot of pH-metric titration of weak base NH₄OH vs strong acid HCl looks lie:

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The Correct Option is A

To determine the correct plot for the pH-metric titration of the weak base NH₄OH with the strong acid HCl, it's important to understand some basic concepts about titrations and pH changes. A titration between a weak base and a strong acid typically exhibits the following characteristics:

1. Initial pH Level: NH₄OH is a weak base, so the initial pH will be above 7 but not very high, since weak bases do not completely dissociate.
2. Addition of Strong Acid (HCl): Adding a strong acid to a weak base will gradually decrease the pH level. The weak base starts neutralizing, and the solution begins to form NH₄^+ ions, which are moderately weak acids.
3. Buffer Region: As titration proceeds, a buffer solution is formed, which resists drastic changes in pH. This occurs when NH₄^+ and OH^- ions are both present in notable concentrations.
4. Equivalence Point: The equivalence point will occur at a pH level lower than 7 (<7) because the strong acid is neutralizing the weak base.
5. Post Equivalence: Past the equivalence point, the solution contains excess HCl, leading to a further decrease in pH, eventually stabilizing as the strong acid dominates.

The correct answer is (A).
NH₄OH is a weak base and HCl is a strong acid. With the addition of HCl to NH₄OH, pH of solution will decrease gradually.
So, the correct graph should be