The concentration of the hydronium ion in hydrochloric acid is 0.0045 M, and the pH of the solution is 2.34.
pH is the potential of the hydrogen or the hydronium ions in the aqueous solution.
As the solution contains [tex]4.5 \times 10^{-3} \;\rm M\;[/tex] HCl the concentration of the hydronium ion will be the same, [tex]4.5 \times 10^{-3} \;\rm M.[/tex]
The pH of the solution is calculated as:
[tex]\begin{aligned} \rm pH &= \rm -log[H^{+}]\\\\&= - \rm log (4.5 \times 10^{-3})\\\\&= 2.34\end{aligned}[/tex]
The concentration of the hydroxide ion is calculated from pH and hydronium ion as:
[tex]\begin{aligned} \rm [H_{3}O^{+}][OH^{-}] &= 10^{-14}\\\\&= \dfrac{1 \times 10^{-14}}{4.5 \times 10^{-3}}\\\\&= 2.2 \times 10^{12}\end{aligned}[/tex]
Now, for the calcium hydroxide solution, the calculations are shown as,
[tex]\begin{aligned} \rm (H_3}\rm O^{+}) &= \rm antilog (-pH)\\\\&= \rm antilog (-8)\\\\&= 10^{-8} \;\rm M\end{aligned}[/tex]
pOH is calculated as:
[tex]\begin{aligned} \rm pOH &= 14- 8 = 6\\\\\rm [OH^{-}] &= \rm antilog (-6)\\\\&= 10^{-6} \end{aligned}[/tex]
The concentration of calcium hydroxide is calculated as:
[tex]\begin{aligned} &= \dfrac{1}{2} \times \rm [OH^{-}]\\\\&= 5 \times 10^{-4} \;\rm M\end{aligned}[/tex]
Therefore, the pH and the pOH give the concentration of the hydrogen or the hydronium ion and the hydroxide ion.
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