Identifikationsaufgabe für unbekannte Substanzen

Identifizierung unbekannter Pulver anhand physikalischer und chemischer Eigenschaften

Qualitative Analysis Intermediate (High School) 75 Min. ~$10,00

Ziel

Mehrere qualitative Tests anwenden, um unbekannte weiße Pulver zu identifizieren und dabei systematisches analytisches Denken zu entwickeln.

Hintergrund

This integrative experiment challenges students to identify unknown white powders from a set of possibilities (NaCl, NaHCO₃, CaCO₃, cornstarch, sugar, baking powder) using a battery of physical and chemical tests. Students must design their own testing sequence, demonstrating understanding of solubility, acid reactivity, flame tests, and indicator tests.

Sicherheitswarnungen

  • Do not taste any unknown samples
  • Wear goggles when heating or adding acid to unknowns
  • Some unknowns may react vigorously with acid

Erforderliche PSA

goggles gloves lab_coat

Materialien

  • Unknown powders (3–5 samples) (2 g each)
    Labeled A, B, C, etc.
  • Dilute HCl (1M) (10 mL)
    For acid reactivity test
  • Distilled water (100 mL)
    For solubility test
  • Iodine solution (5 mL)
    Starch test
  • Universal indicator (5 mL)
    pH test
  • Cobalt chloride paper (5 strips)
    Water of crystallization test

Ausrüstung

Test tubes (10) Bunsen burner Nichrome wire loop Spatula Magnifying glass Evaporating dish

Durchführung

1

Observe each unknown's physical appearance under magnifying glass: crystal shape, texture, color. Record observations.

10 Min.
2

Solubility test: Add 0.5 g of each unknown to 5 mL distilled water. Stir and observe if it dissolves, partially dissolves, or is insoluble.

10 Min.
3

pH test: Add 2 drops of universal indicator to the dissolved/suspended samples. Record the pH.

5 Min.
4

Acid reactivity: Add 5 drops of dilute HCl to a small amount of each dry unknown. Record any effervescence (CO₂ evolution).

10 Min.
5

Iodine test: Add 2 drops of iodine solution to each unknown dissolved in water. Record color change.

5 Min.
6

Flame test: Using a clean nichrome wire, test each unknown in the Bunsen burner flame.

15 Min. Keep face away from flame
7

Heat test: Gently heat a small amount of each unknown in an evaporating dish. Observe melting, charring, or gas evolution.

10 Min. Use tongs to handle hot dish
8

Compile all results and cross-reference to identify each unknown. Write your reasoning.

10 Min.

Erwartete Ergebnisse

NaCl: soluble, neutral pH, no acid reaction, yellow flame. NaHCO₃: soluble, basic pH, effervesces with acid. CaCO₃: insoluble, effervesces with acid, orange-red flame. Cornstarch: insoluble, positive iodine test. Sugar: soluble, chars on heating.

Aufräumen

Dispose of acid-reacted solutions in waste container. Clean all test tubes and glassware. Return unused unknown samples.

Details

Kategorie
Qualitative Analysis
Schwierigkeit
Intermediate (High School)
Dauer
75 Min.
Geschätzte Kosten
$10,00
Schritte
8
Materialien
6

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Frequently Asked Questions

What is the objective of Identifikationsaufgabe für unbekannte Substanzen?
Mehrere qualitative Tests anwenden, um unbekannte weiße Pulver zu identifizieren und dabei systematisches analytisches Denken zu entwickeln.
How difficult is Identifikationsaufgabe für unbekannte Substanzen?
This experiment is rated as Intermediate (High School). It takes approximately 75 minutes to complete.
What safety precautions are needed for Identifikationsaufgabe für unbekannte Substanzen?
Key safety precautions include: Do not taste any unknown samples; Wear goggles when heating or adding acid to unknowns; Some unknowns may react vigorously with acid.
What materials are needed for Identifikationsaufgabe für unbekannte Substanzen?
The main materials required are: Unknown powders (3–5 samples), Dilute HCl (1M), Distilled water, Iodine solution, Universal indicator.
What results should I expect from Identifikationsaufgabe für unbekannte Substanzen?
NaCl: soluble, neutral pH, no acid reaction, yellow flame. NaHCO₃: soluble, basic pH, effervesces with acid. CaCO₃: insoluble, effervesces with acid, orange-red flame. Cornstarch: insoluble, positive iodine test. Sugar: soluble, chars on heating.