CHM Help,please?

[匿名]

2020-04-13 3:04 pm

1) What is the molarity (mol/L) of a potassium permanganate solution if 17.97 mL of it was used to titrate a 11.59 mL sample of a 0.1029 M sodium oxalate standard solution.

2) What is the percent by mass of sodium oxalate in a 0.801 g sample that took 15.27 mL of 0.03282 M potassium permanganate to titrate to a light pink endpoint?

3) What is the percent by mass of oxalate ion in a 0.117 g sample of the iron salt that took 17.85 mL of 0.02 M potassium permanganate to titrate to a light pink endpoint.

Please provider steps with each answer, please and thank you or just example problems similar to each question is fine. I just need help.

回答 (1)

Uncle Michael

2020-04-13 3:34 pm

✔ 最佳答案

1)
2MnO₄⁻ + 16H⁺ + 5C₂O₄²⁻ → 2Mn²⁺ + 8H₂O + 10CO₂

Moles of Na₂C₂O₄ = (0.1029 mol/L) × (11.59/1000 L) = 0.0011926 mol
Moles of KMnO₄ = (0.0011926 mol) × (2/5) = 0.00047704 mol
Molarity of KMnO₄ = (0.00047704 mol) / (17.97/1000 L) = 0.02655 M

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2)
2MnO₄⁻ + 16H⁺ + 5C₂O₄²⁻ → 2Mn²⁺ + 8H₂O + 10CO₂

Moles of KMnO₄ = (0.03282 mol/L) × (15.27/1000 L) = 0.0005012 mol
Moles of Na₂C₂O₄ = (0.0005012 mol) × (5/2) = 0.001253 mol

Molar mass of Na₂C₂O₄ = (23.0×2 + 12.001×2 + 16.0×4) g/mol = 134.0 g/mol
Mass of Na₂C₂O₄ reacted = (0.001253 g) × (134.0 g/mol) = 0.168 g
Percent by mass of Na₂C₂O₄ = (0.168/0.801) × 100% = 21.0%

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3)
What is meant by "oxalate ion in ……. iron salt" ? iron(II) or iron(III) ?

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