standardization?

[匿名]

2020-12-14 11:27 pm

3.A solution of HClO4 was standardized by dissolving 0.4008 g of primary-standard-grade HgO in a solution of KBr:

HgO(s) + 4Br- + H2O HgBr42- + 2OH-

The liberated OH- consumed 43.75 mL of the acid. Calculate the molar concentration of the HClO4.

回答 (1)

Uncle Michael

2020-12-15 12:24 am

✔ 最佳答案

Molar mass of HgO = (200.6 + 16.0) g/mol = 216.6 g/mol

HgO(s) + 4Br⁻ + H₂O → HgBr₄²⁻ + 2OH⁻
Mole ratio HgO : OH⁻ = 1 : 2
Moles of HgO reacted = (0.4008 g) / (216.6 g/mol) = 0.0018504 mol
Moles of OH⁻ produced = (0.0018504 mol) × 2 = 0.0037008 mol

OH⁻ + HClO₄ → H₂O + ClO₄⁻
Mole ratio OH⁻ : HClO₄ = 1 : 1
Moles of OH⁻ = 0.0037008 mol
Moles of HClO₄ = 0.0037008 mol
Molar concentration of HClO₄ = (0.0037008 mol) / (43.75/1000 L) = 0.08459 M

====
OR:
(0.4088 g HgO) × (1 mol HgO / 216.6 g HgO) × (2 mol OH⁻ / 1 mol HgO) × (1 mol HClO₄ / 1 mol OH⁻) / (43.75/1000 L HClO₄ solution)
= 0.08459 M HClO₄

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