Question

Calculate [H+ [CIOJ, and [OH] in an aqueous solution that is 0.170 M in HCIO2 (aq) at 25 °C H* М [CIO; М OH М Is the solution acidic, basic or neutral? acidic basic neutral

Answer 1

$HClO_4$ is a strong acid that completely ionizes to its respective ions in aqueous solution according to the following reaction scheme.

$HClO_4_{(aq)} \rightarrow H^+_{(aq)} + ClO_4^-_{(aq)}$

Hence, each molecule of the acid dissociates into 1 molecule of H+ and one molecule of ClO4-.

We have 0.170 M $HClO_4$.

Hence, the concentrations of H+ and ClO4- ions will be equal to the starting concentration of HClO4.

$[H^+] ={\color{Red} 0.170 \ M}$

$[ClO_4^-] = {\color{Red} 0.170 \ M}$

Now, to calculate the OH- concentration, we will use the ionic product of water at 25 C, which is a constant for all aqueous solutions at 25 C.

$K_w= [H^+][OH^-] = 1.00 \times 10^{-14}$

Hence, the hydroxide ion concentration can be calculated as

$K_w= [H^+][OH^-] = 1.00 \times 10^{-14} \\ \Rightarrow [OH^-] = \frac{1.00 \times 10^{-14}}{0.170 } = {\color{Red} 5.88 \times 10^{-14} \ M}$

Note that $[H^+] >> [OH^-]$ . Hence, there are far more number of H+ ions in the solution than OH- ions. Hence, based on the Bronsted Lowry definition of acid and bases, the solution is an acidic solution as it has more H+ than OH-.

Hence, the correct choice is ${\color{Red} acidic.}$