A Hands-On Experiment with Dissolved CO2
I’ve always wondered about the science behind the things we do every day. I recently set out to measure the ‘fizz’ in soft drinks by finding out how much CO2 is dissolved.
This was a wonderful experiment of titration with sodium hydroxide. It wasn’t procedure following; it was about the Appreciation of the balance between CO2 gas and dissolved CO2.
- Acquiring familiarity with acid-base titrations and endpoint recognition.
- Utilizing stoichiometric calculations to translate titration results to useful CO2 concentrations.
It’s incredible how basic principles of chemistry can account for something as mundane as a fizzy drink! This experience strengthened my interest in analytical chemistry and its real-world applications.
Reactions:
CO2 (dissolved) + H2O ⇌ H2CO3 (carbonic acid)
H2CO3 + 2NaOH → Na2CO3 + 2H2O
Procedure:
- Chill the sample of soft drink to reduce CO2 loss.
- Prepare a standard solution of sodium hydroxide (NaOH) of known concentration.
- Measure accurately a known volume of the chilled soft drink and pour it into an Erlenmeyer flask.
- Add a few drops of phenolphthalein indicator to the flask. The solution will be colorless.
Titrate with NaOH:
- Transfer the standardized NaOH solution into a burette.
- Add NaOH solution from the burette to the soft drink in the Erlenmeyer flask slowly and gently swirl while adding.
- Add NaOH until there is a light, persistent pink color that lasts for at least 30 seconds (endpoint).
- Note the volume of NaOH solution taken to achieve the endpoint.
- Repeat the titration process at least three times for consistency and accuracy.
- Apply stoichiometry and the noted data to determine the concentration of dissolved CO2 in the soft drink (e.g., in g/L).
- Analyze the results and report the dissolved CO2 concentration.
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