Question

Determine the unknown solute from the given observation.
"An unknown solution (pH of $3.5$) was titrated with $0.1$ $M$ $NaOH$, which gives a single equivalence point at pH $7$ on titration curve."

• A. $HF$
• B. $HCl$
• C. $LiOH$
• D. $N{H}_3$
• E. $H_{2}S{O}_4$

Answer 1

Answer: (B)

$HCl$

Since the pH of unknown solute is less than 7, it is an acid.
During titration, a single equivalence point at pH 7 on titration curve is obtained which is characteristic of the titration of strong acid with strong base.
Hence, the unknown solute is HCl, a strong acid.