Weak base + Strong acid yields an acidic salt; pH equivalence point is:

Weak base + Strong acid yields an acidic salt; pH equivalence point is:

• A. less than 7
• B. greater than 7
• C. equal to 7
• D. undefined

Answer: (A)

In titrating a weak base with a strong acid, the equivalence point contains the conjugate acid of the weak base plus the counterion from the strong acid. That conjugate acid tends to donate protons to water, generating hydronium ions and making the solution acidic. For example, titrating ammonia with HCl gives ammonium chloride; NH4+ hydrolyzes to release H3O+, lowering the pH. Therefore the pH at the equivalence point is less than 7.

In titrating a weak base with a strong acid, the equivalence point contains the conjugate acid of the weak base plus the counterion from the strong acid. That conjugate acid tends to donate protons to water, generating hydronium ions and making the solution acidic. For example, titrating ammonia with HCl gives ammonium chloride; NH4+ hydrolyzes to release H3O+, lowering the pH. Therefore the pH at the equivalence point is less than 7.