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Spectroscopy Experiment: Dry Ice Effect on Color Absorbance of pH Indicators

Posted on: October 27th, 2022

In this experiment, we tested the color change of three pH indications from a basic initial state to an acidic final state. The three indicators used were universal indicators, bromocresol green, and phenol red. Dry ice was used to increase the acidity of these solutions. Dry ice is the solid form of carbon dioxide, and when dissolved in water, it produces carbonic acid. Once the carbon acid is formed, the hydrogen atoms dissociate, and the acidity of a system increases. Before adding the dry ice to the solutions, absorbance measurements will be taken to compare the colors of the initial and final solutions.

The smoke that occurs when dry ice is dissolved in water is the carbon dioxide and water vapor that freezes due to the low temperature. The temperature of dry ice is around -77o C. The main use of dry ice in this experiment is to lower the pH of the solutions. A bonus to running this experiment is to see the sublimation of carbon dioxide. Sublimation is the phase transition of a substance from solid to gas and is why, in this case, the final solution outputs fog.


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