Q. Which of the following solutions will have pH=9 at 298 K?
A) $1 \times 10^{- 9}\ M\ HCl\ solution$
B) $1 \times 10^{- 5}\ M\ NaOH\ solution$
C) $1 \times 10^{- 9}\ M\ KOH\ solution$
D) Both (a) and (b)
Explanation
(b)
(a)$pH\ of\ 10^{- 9}\ M\ HCl\ will\ be < 7$
(b)$pOH\ of\ 10^{- 5}M\ NaOH$
$= - \log\left\lbrack {OH}^{-} \right\rbrack$
$= - \log{\left\lbrack 1 \times 10^{- 5} \right\rbrack = 5}$
$pH + pOH = 14$
$pH = 14 - 5 = 9$
(c)$pH\ of\ 10^{- 9}M\ KOH\$will be slightly greater than 7.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.