IB DP Chemistry - Reactivity 3.1 Proton transfer reactions - IB Style Questions For HL Paper 1A -FA 2025
▶️ Answer/Explanation
• A strong base initially has a high pH.
• When a strong acid is added, the pH drops sharply at the equivalence point.
• Graph C shows this typical steep decrease in pH for a strong acid–strong base titration.
✅ Answer: (C)
▶️ Answer/Explanation
Neutralization occurs when an acid reacts with a base to produce a salt and water.
Nitric acid is \(HNO_3\) and calcium hydroxide is \(Ca(OH)_2\).
The balanced neutralization equation is:
\[2HNO_3(aq) + Ca(OH)_2(aq) \rightarrow Ca(NO_3)_2(aq) + 2H_2O(l)\]
The products are therefore calcium nitrate, \(Ca(NO_3)_2\), and water, \(H_2O\).
✅ Answer: (B)
▶️ Answer/Explanation
For any conjugate acid–base pair, the acid dissociation constant \((K_a)\) and base dissociation constant \((K_b)\) are related through the ion-product constant of water, \(K_w\).
The relationship is:
\[K_a \times K_b = K_w\]
Where:
• K_a = acid dissociation constant
• K_b = base dissociation constant
• K_w = \(1.0 \times 10^{-14}\) at 25°C
Therefore, the correct answer is:
✅ Answer: (A)