Titulação Ácido-Base com Fenolftaleína

Determinação da concentração de um ácido usando uma base padrão

Titrations Intermediate (High School) 45 min ~$15,00

Objetivo

Determinar a concentração de uma solução desconhecida de ácido clorídrico titulando-a com uma solução padronizada de hidróxido de sódio, usando fenolftaleína como indicador.

Contexto

This classic acid-base titration demonstrates stoichiometric neutralization. HCl reacts with NaOH in a 1:1 molar ratio. Phenolphthalein turns pink above pH 8.2, providing a clear endpoint. Accurate burette technique and multiple trials are essential for reliable results.

Avisos de segurança

  • NaOH is corrosive — avoid skin and eye contact
  • HCl is corrosive — handle with care
  • Wear safety goggles throughout
  • Wash any spills immediately with water

EPI necessário

goggles gloves lab_coat

Materiais

  • Hydrochloric acid (HCl) (100 mL)
    Unknown concentration
  • Sodium hydroxide (NaOH) (100 mL)
    0.1M standardized
  • Phenolphthalein indicator (5 mL)
    1% in ethanol
  • Distilled water (500 mL)
    For rinsing

Equipamentos

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette Pipette filler White tile Wash bottle

Procedimento

1

Rinse the burette with a small amount of NaOH solution, then fill it to the 0 mL mark. Record the exact starting volume.

5 min Handle NaOH carefully
2

Using the pipette and filler, transfer exactly 25.0 mL of the unknown HCl solution into the Erlenmeyer flask.

3 min
3

Add 2-3 drops of phenolphthalein indicator to the flask. The solution should remain colorless (acidic).

1 min
4

Place the flask on the white tile under the burette. Begin adding NaOH slowly while swirling the flask continuously.

5 min
5

As the endpoint approaches (pink color lingers longer), add NaOH drop by drop until a permanent pale pink color persists for 30 seconds.

5 min
6

Record the final burette reading. Calculate the volume of NaOH used.

2 min
7

Repeat the titration at least two more times for concordant results (within 0.10 mL).

15 min
8

Calculate the concentration of HCl using: C(HCl) = C(NaOH) x V(NaOH) / V(HCl).

5 min

Resultados esperados

The endpoint should show a clear transition from colorless to a persistent pale pink. Concordant titre values (within 0.10 mL) indicate good technique. The calculated concentration should match the expected value within experimental error.

Limpeza

Drain the burette and rinse with distilled water. Neutralize waste solutions before disposal. Rinse all glassware thoroughly.

Detalhes

Categoria
Titrations
Dificuldade
Intermediate (High School)
Duração
45 min
Custo estimado
$15,00
Passos
8
Materiais
4

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Frequently Asked Questions

What is the objective of Titulação Ácido-Base com Fenolftaleína?
Determinar a concentração de uma solução desconhecida de ácido clorídrico titulando-a com uma solução padronizada de hidróxido de sódio, usando fenolftaleína como indicador.
How difficult is Titulação Ácido-Base com Fenolftaleína?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for Titulação Ácido-Base com Fenolftaleína?
Key safety precautions include: NaOH is corrosive — avoid skin and eye contact; HCl is corrosive — handle with care; Wear safety goggles throughout.
What materials are needed for Titulação Ácido-Base com Fenolftaleína?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), Phenolphthalein indicator, Distilled water.
What results should I expect from Titulação Ácido-Base com Fenolftaleína?
The endpoint should show a clear transition from colorless to a persistent pale pink. Concordant titre values (within 0.10 mL) indicate good technique. The calculated concentration should match the expected value within experimental error.