Arc-en-ciel d'Indicateurs de pH

Cartographie des changements de couleur des indicateurs sur toute la gamme de pH

Qualitative Analysis Beginner (Middle School) 45 min ~$8,00

Objectif

Observer comment différents indicateurs de pH changent de couleur à des valeurs de pH spécifiques et comprendre le concept de plages de transition des indicateurs.

Contexte

pH indicators are weak acids or bases whose conjugate forms have different colors. Each indicator has a characteristic transition range where it changes color. By testing multiple indicators across a range of buffered solutions, students create a visual map of indicator behavior that reinforces concepts of acid-base equilibrium and the Henderson-Hasselbalch equation.

Avertissements de sécurité

  • Indicators can stain skin and clothing
  • Extreme pH solutions (pH 1, 14) are corrosive
  • Avoid mixing different buffer solutions

EPI requis

goggles lab_coat

Matériaux

  • Buffer solutions (pH 1–14) (5 mL each)
    Pre-prepared set
  • Methyl orange indicator (5 mL)
    pH 3.1–4.4 range
  • Bromothymol blue indicator (5 mL)
    pH 6.0–7.6 range
  • Phenolphthalein indicator (5 mL)
    pH 8.2–10.0 range
  • Universal indicator (5 mL)
    Full pH range
  • Litmus solution (red and blue) (5 mL each)
    Simple acid/base test

Équipement

Spot plate or microwell plate Dropper pipettes (one per indicator) pH meter or pH paper White background paper

Procédure

1

Arrange the spot plate and add 10 drops of each buffer solution (pH 1 through 14) across each row.

10 min Handle pH 1 and 14 solutions carefully
2

Add 2 drops of methyl orange to the first row of buffer solutions. Record the color at each pH.

5 min
3

Add 2 drops of bromothymol blue to the second row. Record the color at each pH.

5 min
4

Add 2 drops of phenolphthalein to the third row. Record the color at each pH.

5 min
5

Add 2 drops of universal indicator to the fourth row. Observe the full rainbow of colors.

5 min
6

Create a color chart recording each indicator's color at every pH level. Identify each indicator's transition range.

15 min

Résultats attendus

Methyl orange: red (acidic) to yellow (basic) around pH 3–4. Bromothymol blue: yellow to blue around pH 6–7.6. Phenolphthalein: colorless to pink around pH 8–10. Universal indicator: red through violet across the full pH range.

Nettoyage

Pour solutions into the appropriate waste container (acid or base). Rinse spot plates thoroughly with distilled water.

Détails

Catégorie
Qualitative Analysis
Difficulté
Beginner (Middle School)
Durée
45 min
Coût estimé
$8,00
Étapes
6
Matériaux
6

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Frequently Asked Questions

What is the objective of Arc-en-ciel d'Indicateurs de pH?
Observer comment différents indicateurs de pH changent de couleur à des valeurs de pH spécifiques et comprendre le concept de plages de transition des indicateurs.
How difficult is Arc-en-ciel d'Indicateurs de pH?
This experiment is rated as Beginner (Middle School). It takes approximately 45 minutes to complete.
What safety precautions are needed for Arc-en-ciel d'Indicateurs de pH?
Key safety precautions include: Indicators can stain skin and clothing; Extreme pH solutions (pH 1, 14) are corrosive; Avoid mixing different buffer solutions.
What materials are needed for Arc-en-ciel d'Indicateurs de pH?
The main materials required are: Buffer solutions (pH 1–14), Methyl orange indicator, Bromothymol blue indicator, Phenolphthalein indicator, Universal indicator.
What results should I expect from Arc-en-ciel d'Indicateurs de pH?
Methyl orange: red (acidic) to yellow (basic) around pH 3–4. Bromothymol blue: yellow to blue around pH 6–7.6. Phenolphthalein: colorless to pink around pH 8–10. Universal indicator: red through violet across the full pH range.