Kaffeebecher-Kalorimetrie

Messung der Neutralisationsenthalpie mit einem einfachen Kalorimeter

Thermochemistry Intermediate (High School) 40 Min. ~$8,00

Ziel

Die Neutralisationsenthalpie von HCl und NaOH mithilfe eines Polystyrolbecher-Kalorimeters bestimmen.

Hintergrund

A polystyrene cup makes an inexpensive but effective calorimeter because it has low thermal conductivity. By mixing known volumes of acid and base and measuring the temperature change, the enthalpy of neutralization can be calculated. The accepted value for strong acid-strong base neutralization is -57.1 kJ/mol.

Sicherheitswarnungen

  • HCl and NaOH are corrosive
  • Wear safety goggles
  • The mixture will get hot

Erforderliche PSA

goggles gloves lab_coat

Materialien

  • Hydrochloric acid (HCl) (50 mL)
    1M
  • Sodium hydroxide (NaOH) (50 mL)
    1M
  • Distilled water (100 mL)
    For calibration

Ausrüstung

Two polystyrene (Styrofoam) cups (nested) Cardboard lid with hole Thermometer (0.1°C resolution) Graduated cylinder (50 mL) Stopwatch

Durchführung

1

Measure 50 mL of 1M HCl and pour into the nested polystyrene cups. Record the initial temperature every 30 seconds for 3 minutes.

5 Min. HCl is corrosive
2

Measure 50 mL of 1M NaOH in a separate container. Record its temperature.

2 Min. NaOH is corrosive
3

Quickly pour the NaOH into the HCl, stir gently, and replace the lid with thermometer.

1 Min. Exothermic reaction
4

Record the temperature every 30 seconds for 5 minutes. Note the maximum temperature.

5 Min.
5

Plot temperature vs time. Extrapolate the cooling curve back to the mixing time to find the corrected maximum temperature.

5 Min.
6

Calculate ΔT, then q = mcΔT (assume c = 4.18 J/g°C, mass = 100 g). Calculate ΔH per mole of water formed.

8 Min.

Erwartete Ergebnisse

Temperature should rise by approximately 6-7°C. Calculated ΔH should be approximately -50 to -57 kJ/mol (accepted: -57.1 kJ/mol). Losses to the calorimeter walls typically give lower values.

Aufräumen

The neutralized solution is safe to pour down the drain. Rinse and dry the calorimeter cups for reuse.

Details

Kategorie
Thermochemistry
Schwierigkeit
Intermediate (High School)
Dauer
40 Min.
Geschätzte Kosten
$8,00
Schritte
6
Materialien
3

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Frequently Asked Questions

What is the objective of Kaffeebecher-Kalorimetrie?
Die Neutralisationsenthalpie von HCl und NaOH mithilfe eines Polystyrolbecher-Kalorimeters bestimmen.
How difficult is Kaffeebecher-Kalorimetrie?
This experiment is rated as Intermediate (High School). It takes approximately 40 minutes to complete.
What safety precautions are needed for Kaffeebecher-Kalorimetrie?
Key safety precautions include: HCl and NaOH are corrosive; Wear safety goggles; The mixture will get hot.
What materials are needed for Kaffeebecher-Kalorimetrie?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Distilled water.
What results should I expect from Kaffeebecher-Kalorimetrie?
Temperature should rise by approximately 6-7°C. Calculated ΔH should be approximately -50 to -57 kJ/mol (accepted: -57.1 kJ/mol). Losses to the calorimeter walls typically give lower values.