Question

In the titration of $NaOH$ and $HCl$, which of the following indicator will be used?

• A. Methyl orange
• B. Methyl red
• C. Both $A$ and $B$
• D. None of the above

Answer 1

The correct option is D None of the above

$HCl$ is a strong acid and $NaOH$ is a strong base. Therefore, titrating one against the other yields a complete reaction. The titration is complete when the $pH$ reaches $7.0$. Methyl orange would not be appropriate here, as the color change occurs at between $3.1$ and $4.4$ in an aqueous solution. Not helpful in this case. A much better choice here would be phenolphthalein, which goes from clear to pink at a $pH$ of $8.2$ still not exactly $7.0$, but well within the rapid transition point curve.