Doppelindikator-Titration eines Carbonat-Bicarbonat-Gemisches

Analyse eines Carbonatgemisches mit zwei Indikatoren

Titrations Advanced (University) 55 Min. ~$14,00

Ziel

Ein Gemisch aus Natriumcarbonat und Natriumbicarbonat durch Titration mit HCl unter sequenziellem Einsatz zweier Indikatoren – Phenolphthalein und Methylorange – analysieren.

Hintergrund

A mixture of Na₂CO₃ and NaHCO₃ has two equivalence points when titrated with acid. Phenolphthalein detects the first (CO₂³⁻ → HCO₃⁻), and methyl orange detects the second (HCO₃⁻ → H₂CO₃). By comparing the volumes at each endpoint, the individual concentrations can be calculated.

Sicherheitswarnungen

  • HCl is corrosive
  • Wear safety goggles throughout
  • Handle indicators carefully — they stain

Erforderliche PSA

goggles lab_coat

Materialien

  • Sodium carbonate/bicarbonate mixture (100 mL)
    Unknown composition
  • Hydrochloric acid (HCl) (100 mL)
    0.1M standardized
  • Phenolphthalein indicator (5 mL)
  • Methyl orange indicator (5 mL)
  • Distilled water (200 mL)

Ausrüstung

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette White tile

Durchführung

1

Pipette 25.0 mL of the carbonate/bicarbonate mixture into the flask.

2 Min.
2

Add 2-3 drops of phenolphthalein. The solution should turn pink.

1 Min.
3

Fill the burette with 0.1M HCl. Record the initial volume.

3 Min.
4

Titrate until the pink color disappears (first endpoint). Record volume V₁.

10 Min.
5

Without refilling the burette, add 2-3 drops of methyl orange to the same flask.

1 Min.
6

Continue titrating until the color changes from yellow to orange/salmon (second endpoint). Record total volume V₂.

10 Min.
7

Repeat the entire process for concordant results.

18 Min.
8

Calculate: V(phenolphthalein) = V₁, V(methyl orange only) = V₂ - V₁. Use these to find the individual concentrations of Na₂CO₃ and NaHCO₃.

7 Min.

Erwartete Ergebnisse

V₁ corresponds to the carbonate content, and (V₂ - V₁) includes both the remaining carbonate reaction and the original bicarbonate. For pure carbonate, V₂ - V₁ = V₁. Any excess indicates bicarbonate present.

Aufräumen

Neutralize waste solutions before disposal. Rinse all glassware thoroughly.

Details

Kategorie
Titrations
Schwierigkeit
Advanced (University)
Dauer
55 Min.
Geschätzte Kosten
$14,00
Schritte
8
Materialien
5

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Frequently Asked Questions

What is the objective of Doppelindikator-Titration eines Carbonat-Bicarbonat-Gemisches?
Ein Gemisch aus Natriumcarbonat und Natriumbicarbonat durch Titration mit HCl unter sequenziellem Einsatz zweier Indikatoren – Phenolphthalein und Methylorange – analysieren.
How difficult is Doppelindikator-Titration eines Carbonat-Bicarbonat-Gemisches?
This experiment is rated as Advanced (University). It takes approximately 55 minutes to complete.
What safety precautions are needed for Doppelindikator-Titration eines Carbonat-Bicarbonat-Gemisches?
Key safety precautions include: HCl is corrosive; Wear safety goggles throughout; Handle indicators carefully — they stain.
What materials are needed for Doppelindikator-Titration eines Carbonat-Bicarbonat-Gemisches?
The main materials required are: Sodium carbonate/bicarbonate mixture, Hydrochloric acid (HCl), Phenolphthalein indicator, Methyl orange indicator, Distilled water.
What results should I expect from Doppelindikator-Titration eines Carbonat-Bicarbonat-Gemisches?
V₁ corresponds to the carbonate content, and (V₂ - V₁) includes both the remaining carbonate reaction and the original bicarbonate. For pure carbonate, V₂ - V₁ = V₁. Any excess indicates bicarbonate present.