Session: General Posters:

In the past two centuries the CO₂concentration has increased in the atmosphere as the result of human activities. High CO₂concentration and its related “carbon problem” has gained increasing attention in the scientific communities. One of the carbon related problems is “ocean acidification”. The oceans serve as a carbon sink and the amount of CO₂absorbed by the ocean increases proportional to the levels of atmospheric CO₂. The dissolved CO₂and water combine to form carbonic acid, that its dissociation results indecrease in the pH of ocean's surface. Considering the pH value of the ocean, this change represents about 30% increase in ocean acidity. Herein we describe an indicator-based color change to highlight and visualize the ocean acidification by CO₂absorption through the air. This demonstration consists of putting a beaker of “soda water” in a closed container next to the bakers include tap water and distilled water containing acid base indicators. The color change of indicator before and after exposure to different volume of CO₂(Fig 1) indicates the acidification.
Using universal indicator allowed to demonstrate how acidic the solutions get upon exposure to high CO₂contents. The use of the phenol red, with pKa around the pH of ocean's surface, enable to track the minimal pH changes. Various CO₂sources including combustion and CO₂tank, and variety of measurement techniques have been utilized to measure the effect of absorbed CO₂into the water.¹However, using soda water as an obvious CO₂source,² enabled an engaging general chemistry laboratory experiment exploring the equilibration and transferring acidity through the air. Using different indicators revealed also the importance of choosing the right acid-base indicator for accurate validation of pH changes.

<b>Fig 1. </b>Color changes of phenol red and universal indicators in DI water and tap water before and after exposure to CO<sub>2</sub>.

Fig 1. Color changes of phenol red and universal indicators in DI water and tap water before and after exposure to CO₂.

Lida Khalafi

Assistant Professor of Chemistry, Avila University

Appearances