PH explanation?

👨🏻‍🏫 學術台化學

[匿名]

2016-02-27 6:12 pm

更新1:

A buffer is prepared by adding 48.3 mL of 0.63 M NaF to 33.7 mL of 0.49 M HF. What is the pH of the final solution? Ka for HF = 6.8×10-4 pH =

回答 (2)

賣女孩的火柴

2016-02-27 6:26 pm

✔ 最佳答案

HF(aq) + H₂O(l) ⇌ H₃O⁺(aq) + F⁻(aq)

After mixing :
[HF] = 0.49 × {(33.7)/(33.7 + 48.3)} = 0.49 × 33.7 / 82.0 M
[F⁻] = 0.63 × {(48.3)/(33.7 + 48.3)} = 0.63 × 48.3 / 82.0 M

pH = pKa - log([HF]/[F⁻])
pH = -log(6.8 × 10⁻⁴) - log{(0.49 × 33.7)/(0.63 × 48.3)}
pH = 3.4