Question

The $P^H$ of $HCl$ is $5$. It is diluted by $1000$ times. Its $P^H$ will be:

• A. $5$
• B. $8$
• C. $2$
• D. $6-7$

Answer 1

The correct option is D $6-7$

According to Arrenhius rule : $pH=-log$ [$H^{+}$]

Where $H^{+}$ is the concentration of acid, initially

$5$= -log [$H^{+}$

[ $H^{+}$]=$10^{-5}$

when we dilute 1000 times, the concentration decreases 1000 times because the concentration is inversely proportional to volume.

Final [ $H^{+}$] =$10^{-5}$/1000 =$10^{-7}$

Now,$pH$ = - log [$H^{+}$]

$-log$($10^{-7}$) = 6.69 $\approx$ 7