$50.0 mL$ of $0.100 M$ $HClO X_{4}$ and $50.0 mL$ of $0.300 M$ $HNO X_{3}$ are mixed in water. Treating both as completely ionised (levelled to $H X_{3} O X^{+}$ ), the pH of the mixture is

Answer: C

Total

H X_{3} O X^{+}

moles

= 50.0 \times 0.100 + 50.0 \times 0.300 = 20.0 mmol

100.0 mL

, so

[H X_{3} O X^{+}] = 0.200 M

pH = - lo g 0.200 = 0.70

. The value

0.40

comes from forgetting to dilute, and

1.00

from using only the

HClO X_{4}

concentration.