What is the pH at the equivalence point in the titration of 100 mL of 0.10 M HCl with 0.10 M NaOH?

• A. 9.00
• B. 7.00
• C. 5.00
• D. 1.00

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of equivalence point in a titration. The equivalence point is reached when the amount of titrant added is stoichiometrically equal to the amount of analyte present. In this case, HCl (a strong acid) is being titrated with NaOH (a strong base).
2. Step 2: Recognize that the reaction between HCl and NaOH is a neutralization reaction: ${H\mathrm{Cl}}_{(aq)}+{\mathrm{Na}\mathrm{OH}}_{(aq)}\to {\mathrm{Na}\mathrm{Cl}}_{(aq)}+{H2}_O$. Both HCl and NaOH are strong electrolytes, meaning they completely dissociate in water.
3. Step 3: At the equivalence point, all the HCl has reacted with NaOH to form water and NaCl. Since both the acid and base are strong, the resulting solution contains only water and a neutral salt (NaCl), which does not affect the pH.
4. Step 4: Recall that the pH of pure water at 25°C is 7.00, as it is neutral. At the equivalence point in this titration, the solution is effectively pure water with dissolved NaCl, which does not alter the pH.
5. Step 5: Conclude that the pH at the equivalence point in the titration of a strong acid (HCl) with a strong base (NaOH) is always 7.00 under standard conditions (25°C).