Question

A 75.00-mL portion of a solution that is 0.0460 M inis treated with 150.00 mL of 0.0230 M KOH (aq). Is the pH of the resulting mixture greater than, less than, or equal to 7.0? Explain.

Short answer

The pH of the resulting mixture is neutral, that is, seven.

Step-by-step solution

pH Scale.

pH means the potential of hydrogen. The pH scale helps in determiningif the given solution is acidic, basic, or neutral. The pH scale ranges from 0 to 7 and 7 to 14. If thesolution is acidic, the pH is between 0 and 6. If the solution is neutral, then it shows seven pH. If the solution is basic, the pH is between 8 and 14.

Reaction between HClO4 and KOH.

When HClO4 reacts with the potassium hydroxide, it forms $Cl{O}_4^{-}$ ions, K⁺ ions, and water, as below.

$HCl{O}_4\left(aq\right)+KOH\left(aq\right)\leftrightharpoons Cl{O}_4^{-}\left(aq\right)+K^{+}\left(aq\right)+H_{2}O\left(l\right)$

The pH calculation.

Here, 0.0460 M HClO₄ is given, and 0.0230 M of KOH is given.

HClO₄ = 0.075 L × 0.0460 M = 0.00345 moles.

KOH = 0.150 L × 0.0230 M = 0.00345 moles.

The numbers of mols of each are equal, and because of this they neutralize each other, so the pH is 7.