Calorimetria em Copo de Café

Medição da entalpia de neutralização usando um calorímetro simples

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

Objetivo

Determinar a entalpia de neutralização de HCl e NaOH usando um calorímetro de copo de poliestireno.

Contexto

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.

Avisos de segurança

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

EPI necessário

goggles gloves lab_coat

Materiais

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

Equipamentos

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

Procedimento

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

Resultados esperados

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.

Limpeza

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

Detalhes

Categoria
Thermochemistry
Dificuldade
Intermediate (High School)
Duração
40 min
Custo estimado
$8,00
Passos
6
Materiais
3

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Frequently Asked Questions

What is the objective of Calorimetria em Copo de Café?
Determinar a entalpia de neutralização de HCl e NaOH usando um calorímetro de copo de poliestireno.
How difficult is Calorimetria em Copo de Café?
This experiment is rated as Intermediate (High School). It takes approximately 40 minutes to complete.
What safety precautions are needed for Calorimetria em Copo de Café?
Key safety precautions include: HCl and NaOH are corrosive; Wear safety goggles; The mixture will get hot.
What materials are needed for Calorimetria em Copo de Café?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Distilled water.
What results should I expect from Calorimetria em Copo 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.