Finding mols?

👨🏻‍🏫 學術台化學

[匿名]

2016-02-27 6:18 pm

更新1:

How many moles of sodium acetate must be added to 2.0 L of 0.10 M acetic acid to give a solution that has a pH equal to 4.80? Ignore the volume change due to the addition of sodium acetate. Ka of acetic acid is 1.7×10-5. Mol NaOAc =

回答 (1)

賣女孩的火柴

2016-02-27 6:52 pm

✔ 最佳答案

CH₃COOH(aq) + H₂O(l) ⇌ CH₃COO⁻(aq) + H₃O⁺(aq)

At eqm :
[CH₃COOH]≈ 0.1 M

pH = pKa - log([CH₃COOH]/[CH₃COO⁻])
4.80 = -log(1.7 × 10⁻⁵) - log(0.1/[CH₃COO⁻])
4.80 = -log(1.7 × 10⁻⁵) - log0.1 + log[CH₃COO⁻]
log[CH₃COO⁻] = 4.80 + log(1.7 × 10⁻⁵) + log0.1
[CH₃COO⁻] = 10^{4.80 + log(1.7 × 10⁻⁵) + log0.1} = 0.107 M

No. of moles of CH₃COONa added = 0.107 × 2 = 0.214 mol

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