Answer:
pH = 7.73
Step-by-step explanation:
The pKa of the HOCl/KOCl buffer is 7.46. To determine the pH of this buffer we can use H-H equation:
pH = pKa + log [A⁻] / [HA]
pH = 7.46 + log [KOCl] / [HOCl]
Where [] is molarity -or moles- of each compound
Initial moles of HClO and NaClO:
HOCl: 0.500L * (0.12mol / L) = 0.06 moles HOCl
KOCl: 0.500L * (0.080mol / L) = 0.04 moles KOCl
Now, HOCl reacts with KOH producing KOCl:
HOCl + KOH → KOCl + H₂O
The moles of KOH in the reaction are:
2.5x10⁻³L * (10mol /L) = 0.025 moles KOH
That means after the reaction, 0.025 moles of HOCl are consumed and 0.025 moles of KOCl are produced.
And after the reaction, moles are:
Final moles:
HOCl: 0.06mol - 0.025mol = 0.035 mol
KOCl: 0.04mol + 0.025mol = 0.065 mol
Replaing in H-H equation:
pH = 7.46 + log [0.065mol] / [0.035mol]
pH = 7.73