Calorimétrie en Gobelet de Café

Mesure de l'enthalpie de neutralisation avec un calorimètre simple

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

Objectif

Déterminer l'enthalpie de neutralisation de HCl et NaOH en utilisant un calorimètre en gobelet de polystyrène.

Contexte

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.

Avertissements de sécurité

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

EPI requis

goggles gloves lab_coat

Matériaux

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

Équipement

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

Procédure

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

Résultats attendus

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.

Nettoyage

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

Détails

Catégorie
Thermochemistry
Difficulté
Intermediate (High School)
Durée
40 min
Coût estimé
$8,00
Étapes
6
Matériaux
3

Plus d'expériences

Capacité Calorifique Spécifique des Métaux 40 min Chaleur de Combustion du Magnésium 50 min Chimie des Poches de Froid 20 min Cristallisation Exothermique de l'Acétate de Sodium 30 min Démonstration de Réaction Endothermique 20 min Enthalpie de Fusion de la Glace 25 min La Dissolution n'Est Pas Toujours Exothermique 25 min Simulation de Calorimétrie en Bombe 45 min Vérification de la Loi de Hess 60 min

Frequently Asked Questions

What is the objective of Calorimétrie en Gobelet de Café?
Déterminer l'enthalpie de neutralisation de HCl et NaOH en utilisant un calorimètre en gobelet de polystyrène.
How difficult is Calorimétrie en Gobelet de Café?
This experiment is rated as Intermediate (High School). It takes approximately 40 minutes to complete.
What safety precautions are needed for Calorimétrie en Gobelet de Café?
Key safety precautions include: HCl and NaOH are corrosive; Wear safety goggles; The mixture will get hot.
What materials are needed for Calorimétrie en Gobelet de Café?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Distilled water.
What results should I expect from Calorimétrie en Gobelet de Café?
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.